solving simple equations

1.1 Solving Simple Equations

1.2 Solving Multi-Step Equations

1.3 Solving Equations with Variables on Both Sides

1.4 Rewriting Equations and Formulas

EquationsEquations

STEAM Video: “Training for a Half Marathon”

Chapter Learning Target: Understand equations.

Chapter Success Criteria: ■■ I can identify key words and phrases to

solve equations.■■ I can write word sentences as equations.■■ I can explain how to solve equations.■■ I can model different types of equations

to solve real-life problems.

ms2019_gr8_se_01.indb iims2019_gr8_se_01.indb ii 1/19/18 10:45 AM1/19/18 10:45 AM

11111111111

Performance Task

STEAM Video Training for a Half Marathon

A half marathon is a race that is 13.1 miles long. How can a runner develop a routine to help train for a half marathon?

Watch the STEAM Video “Training for a Half Marathon.” Th en answer the following questions.

1. Alex and Enid are training for a half marathon. Th ey run four days each week, as shown in the table. How far do they have to run on Saturday to average 4.75 miles per running day in Week Nine?

2. Assuming they meet their goal on Saturday in Week Nine, what is the average number of miles per running day over the 4 weeks in the table?

Distance Ran (miles)

Monday Wednesday Friday Saturday

Week Six 2.5 2.6 2.4 7.0

Week Seven 3.3 2.8 2.9 7.0

Week Eight 3.3 3.1 2.6 8.5

Week Nine 3.7 3.0 4.1 x

Target Heart Rates

After completing this chapter, you will be able to use the concepts you learned to answer the questions in the STEAM Video Performance Task. You will be given information about a person’s heart rate.

Resting heart rate

Day 1 = x

Day 2 = x

Day 3 = x 5-day average = 62

Day 4 = x

Day 5 = 58

You will be asked to fi nd the range of a person’s target heart rate. What factors might aff ect the range of a person’s target heart rate?

Big Ideas Math: Modeling Real Life Grade 8 Copyright © Big Ideas Learning, LLC

Assessment Book

All rights reserved.

18

Chapter

1 Performance Task (continued) Name _________________________________________________________ Date _________

Target Heart Rates

4. The Karvonen Formula calculates a person’s target heart rate for different intensity

levels of exercise. Your friend can find her target heart rate t by adding her resting

heart rate to the product of her heart rate reserve and her percent of intensity i

(in decimal form). Write the Karvonen Formula.

5. Your friend uses the Karvonen Formula to find the upper and lower limit of her

target heart rate range.

a. The upper limit of her target heart rate range is found using an intensity level

of 80%. Write an equation for her upper limit u.

b. The lower limit of her target heart rate range is found using an intensity level

of 60%. Write an equation for her lower limit .

6. If your friend’s doctor wants her target heart rate to be between 143 and 170, and her

average resting heart rate is 62, what is her age? Explain your method.

Copyright © Big Ideas Learning, LLC

Big Ideas Math: Modeling Real Life Grade 8

All rights reserved.

Assessment Book 17

Chapter 1 Performance Task

Name _________________________________________________________ Date __________

Target Heart Rates Doctors recommend staying within a target heart rate range when training for an athletic

endeavor like a half marathon. How can you use simple equations to calculate that range?

Your friend is training to run a half marathon. She talks to her doctor about how to train

safely. Her doctor gives her an assignment to do before the race so that she will know

whether she is exerting herself too hard. The doctor tells her about the Karvonen Formula,

which will help her determine when her heart rate is in its target range.

1. Your friend finds her resting heart rate by counting her pulse for one minute

immediately after she wakes up for 5 days in a row. She finds her average resting

heart rate to be 62 over 5 days, and she remembers that the last day’s pulse was

58 and all the others were the same. Find her pulse on all the other days. Justify

your answer by showing your steps.

2. Your friend finds her maximum heart rate m by subtracting her age a from 220.

Write an equation that she can use to find m.

3. Your friend finds her “heart rate reserve” h by subtracting her average resting

heart rate r from her maximum heart rate m. Write an equation that she can use

to find h.

ms2019_gr8_se_01.indb 1ms2019_gr8_se_01.indb 1 1/19/18 10:45 AM1/19/18 10:45 AM

2222222222222222222222

Getting Ready for Chapter

Chapter Exploration

Vocabulary

1. Work with a partner. Use algebra tiles to model and solve each equation.

a. x + 3 = −3

= Model the equation x + 3 = −3.

= Add three −1 tiles to each side.

= Remove the zero pairs from the left side.

= Write the solution of the equation.

b. −3 = x − 2

= Model the equation −3 = x − 2.

= Add two +1 tiles to each side.

= Remove the zero pairs from the each side.

= Write the solution of the equation.

c. x − 4 = 1 d. x + 5 = −2 e. −7 = x + 4

f. x + 6 = 7 g. −5 + x = −3 h. −4 = x − 4

2. WRITE GUIDELINES Work with a partner. Use your models in Exercise 1 to summarize the algebraic steps that you can use to solve an equation.

Th e following vocabulary term is defi ned in this chapter. Th ink about what the term might mean and record your thoughts.

literal equation

−= +1+ = −1 = x


EXPLORATION 1EXPLORATION 1

Section 1.1 Solving Simple Equations 3

Solving Simple EquationsSolving Simple Equations1.1Learning Target: Write and solve one-step equations.

Success Criteria: • I can apply properties of equality to produce equivalent equations. • I can solve equations using addition, subtraction, multiplication, or division. • I can use equations to model and solve real-life problems.

Using Properties of Equality

Work with a partner.

a. You have used the following properties in a previous course. Explain the meaning of each property.

• Addition Property of Equality

• Subtraction Property of Equality

• Multiplication Property of Equality

• Division Property of Equality

b. Which property can you use to solve each of the equations modeled by the algebra tiles? Solve each equation and explain your method.

=

=

=

c. Write an equation that can be solved using one property of equality. Exchange equations with another pair and fi nd the solution.

Recognize Usefulness of ToolsCan you use algebra tiles to solve any equation? Explain your reasoning.

Math Practice

−= +1+= −1

= variable

= −variable


4 Chapter 1 Equations

1.1 Lesson

Addition Property of EqualityWords Adding the same number to each side of an equation

produces an equivalent equation.

Algebra If a = b, then a + c = b + c.

Subtraction Property of EqualityWords Subtracting the same number from each side of an equation


Algebra If a = b, then a − c = b − c.

Key Ideas

RememberAddition and subtraction are inverse operations.

Solving Equations Using Addition or SubtractionEXAMPLE 1

a. Solve x − 7 = −6.

x − 7 = −6 Write the equation.

+ 7 + 7 Addition Property of Equality

x = 1 Simplify.

Th e solution is x = 1.

b. Solve 1 = w + 6.

1 5 w 1 6 Write the equation.

− 6 − 6 Subtraction Property of Equality

−5 = w Simplify.

Th e solution is w = −5.

c. Solve y + 3.4 = 0.5.

y + 3.4 = 0.5 Write the equation.

− 3.4 − 3.4 Subtraction Property of Equality

y = −2.9 Simplify.

Th e solution is y = −2.9.

Try It Solve the equation. Check your solution.

1. b + 2 = −5 2. −3 = k + 3 3. t − 1

— 4

= − 3

— 4

Undo the subtraction.

Check

1 = w + 6

1 =? −5 + 6

1 = 1 ✓

Undo the addition.

Undo the addition.

Check

x − 7 = −6

1 − 7 =? −6

−6 = −6 ✓



Multiplication Property of EqualityWords Multiplying each side of an equation by the same number


Algebra If a = b, then a ⋅ c = b ⋅ c.

Division Property of EqualityWords Dividing each side of an equation by the same number


Algebra If a = b, then a ÷ c = b ÷ c, c ≠ 0.

Key Ideas

Solving Equations Using Multiplication or DivisionEXAMPLE 2

a. Solve − 3

— 4

n = −2.

− 3

— 4

n = −2 Write the equation.

− 4

— 3

⋅ ( − 3

— 4

n ) = − 4

— 3

⋅ (−2) Multiplication Property of Equality

n = 8 — 3

Simplify.

Th e solution is n = 8

— 3

.

b. Solve 𝛑 x = 3𝛑.

π x = 3π Write the equation.

π x

— π

= 3π

— π

Division Property of Equality

x = 3 Simplify.



4. y — 4

= −7 5. − 2z

— 3

= 6

6. 0.09w = 1.8 7. 6π = π x

Multiply by the reciprocal.

Check

πx = 3π

π(3) =? 3π

3π = 3π ✓

Undo the multiplication.

RememberMultiplication and division are inverse operations.



Self-Assessment for Concepts & Skills

Solve each exercise. Th en rate your understanding of the success criteria in your journal.

WRITING Are the equations equivalent? Explain.

10. x + 3 = 4 and x = 1 11. − y —

5 = 2 and y = 10

12. OPEN-ENDED Write an equation that you can use the Division Property of Equality to solve.

SOLVING EQUATIONS Solve the equation. Check your solution.

13. −5 = w − 3 14. − 2

— 3

n = 8

15. p − 9 ÷ 1

— 3

= 6 16. q + ∣ 3 ∣ = − 5

17. WHICH ONE DOESN’T BELONG? Which equation does not belong with the other three? Explain your reasoning.

x − 2 = 4 x − 3 = 9 x − 5 = 1 x − 6 = 0

Identifying the Solution of an EquationEXAMPLE 3

What value of k makes the equation k + 4 ÷ 0.2 = 5 true?

A. −15 B. −5 C. −3 D. 1.5

k + 4 ÷ 0.2 = 5 Write the equation.

k + 20 = 5 Divide 4 by 0.2.


k = −15 Simplify.

Th e correct answer is A.


8. p − 8 ÷ 1

— 2

= −3 9. q + ∣ −10 ∣ = 2

Check

k + 4 ÷ 0.2 = 5

−15 + 4 ÷ 0.2 =? 5

−15 + 20 =? 5

5 = 5 ✓



Self-Assessment for Problem SolvingSolve each exercise. Th en rate your understanding of the success criteria in your journal.

18. A shipwreck is 300 meters away from a diving station. An undersea explorer travels away from the station at a speed of 2 meters per second. Th e explorer is x meters away from the station and will reach the shipwreck in 100 seconds. What is the value of x?

19. You conduct an inventory for a hardware store and count 40 rolls of duct tape. Your manager wants to keep 7 boxes of duct tape in stock. If each box holds 8 rolls of duct tape, how many boxes should you order? Justify your answer.

20. DIG DEEPER Your fi tness tracker overestimates the number of steps you take by 5%. Th e tracker indicates that you took 7350 steps today. Write and solve an equation to fi nd the actual number of steps you took today.

Th e temperature in a crater on Mars is 0°C at 1 p.m. Th e temperature decreases 8°C every hour. When will the temperature be −50°C?

To determine when the temperature will be −50°C, fi nd how long it will take the temperature to decrease by 50°C. Write and solve an equation to fi nd the time.

Verbal Model

Variable Let t be the time for the temperature to decrease 50°C.

Equation −50 = −8 • t

−50 = −8t Write the equation.

−50

— −8

= −8t

— −8


6.25 = t Simplify.

Th e temperature will be −50°C at 6.25 hours after 1 p.m., or 6 hours and 15 minutes after 1 p.m.

So, the temperature will be −50°C at 7:15 p.m.

Modeling Real LifeEXAMPLE 4

Change in temperature

(°C)

Time(hours)=

Hourly change in temperature(°C per hour)

•

The changes in temperature are negative because the temperatures are decreasing.



Go to BigIdeasMath.com to get HELP with solving the exercises.

1.1 Practice

Review & RefreshEvaluate the expression.

1. (32 − 8) + 4 2. 1 + 5 × 32 3. 4 × 3 + 102

Identify the terms, coeffi cients, and constants in the expression.

4. 11q + 2 5. h + 9 + g 6. 6m2 + 7n

Write the phrase as an expression.

7. the quotient of 22 and a number a

8. the diff erence of a number t and 9

Concepts, Skills, & Problem SolvingUSING PROPERTIES OF EQUALITY Which property of equality can you use to solve the equation modeled by the algebra tiles? Solve the equation and explain your method. (See Exploration 1, p. 3.)

9. =

10. =

SOLVING EQUATIONS USING ADDITION OR SUBTRACTION Solve the equation. Check your solution.

11. x + 12 = 7 12. g − 16 = 8 13. −9 + p = 12

14. 2.5 + y = −3.5 15. x − 8π = π 16. 4π = w − 6π

17. 5

— 6

= 1

— 6

+ d 18. 3

— 8

= r + 2

— 3

19. n − 1.4 = −6.3

20. MODELING REAL LIFE A discounted concert ticket costs $14.50 less than the original price p. You pay $53 for a discounted ticket. Write and solve an equation to fi nd the original price.

21. PROBLEM SOLVING A game of bowling has ten frames. After fi ve frames, your friend’s bowling score is 65 and your bowling score is 8 less than your friend’s score.

a. Write and solve an equation to fi nd your score.

b. By the end of the game, your friend's score doubles and your score increases by 80. Who wins the game? Explain.



SOLVING EQUATIONS USING MULTIPLICATION OR DIVISION Solve the equation. Check your solution.

22. 7x = 35 23. 4 = −0.8n 24. 6 = − w

— 8

25. m

— π

= 7.3 26. −4.3g = 25.8 27. 3

— 2

= 9

— 10

k

28. −7.8x = −1.56 29. −2 = 6

— 7

p 30. 3π d = 12π

31. YOU BE THE TEACHERYOU BE THE TEACHER Your friend solves theequation. Is your friend correct? Explain your reasoning.

32. STRUCTURE A gym teacher orders 42 tennis balls. Th e tennis balls come in packs of 3. Which of the following equations represents the number x of packs?

x + 3 = 42

3x = 42

x

— 3

= 42

x = 3

— 42

33. MODELING REAL LIFE You clean a community park for 6.5 hours. You earn $42.25. How much do you earn per hour?

34. MODELING REAL LIFE A rocket is scheduled to launch from a command center in 3.75 hours. What time is it now?

35. MODELING REAL LIFE After earning interest, the balance of an account is $420. Th e new balance

is 7

— 6

of the original balance. How much interest

did it earn?

36. MODELING REAL LIFE After a cleanup, algae covers 2 miles of a coastline. Th e length of the coastline

covered after the cleanup is 1

— 3

of the previous length.

How many miles of the coast did the algae previously cover?

37. PROBLEM SOLVING Cedar Point, an amusement park, has some of the tallest roller coasters in the United States. Th e Mantis is 165 feet shorter than the Millennium Force. What is the height of the Mantis?

Launch Time11:20 A.M.

Roller Coasters at Cedar Point

Coaster Height (feet)

Top Th rill Dragster 420

Millennium Force 310

Valravn 225

Mantis ?

−1.5 + k = 8.2k = 8.2 + (−1.5)k = 6.7



SOLVING AN EQUATION Solve the equation. Check your solution.

38. −3 = h + 8 ÷ 2 39. 12 = w − ∣ −7 ∣ 40. q + ∣ 6.4 ∣ = 9.6

41. d − 2.8 ÷ 0.2 = −14 42. 8

— 9

= x + 1

— 3

(7) 43. p − 1

— 4

⋅ 3 = − 5

— 6

44. GEOMETRY Th e volume V of the prism is 1122 cubic inches. Use the formula V = Bh to fi nd the height h of the prism.

SOLVING AN EQUATION Write and solve an equation to fi nd the value of x.

45. Th e angles are complementary. 46. Th e angles are supplementary.

45°x°

50°x°

47. CRITICAL THINKING Which of the operations +, −, ×, and ÷ are inverses of each other? Explain.

48. LOGIC Without solving, determine whether the solution of −2x = −15 is greater than or less than −15. Explain.

49. OPEN-ENDED Write a subtraction equation and a division equation so that each has a solution of −2. Justify your answer.

50. MODELING REAL LIFE Ants of a particular species can carry 50 times their body weight. It takes 32 ants of that species to carry the cherry shown. About how much does each ant weigh?

51. REASONING One-fourth of the girls and one-eighth of the boys in a grade retake their school pictures. Th e photographer retakes pictures for 16 girls and 7 boys. How many students are in the grade?

52. DIG DEEPER You use a crowdfunding website to raise money. Th e website keeps 5% of each donation. Five of your friends each donate the same amount. Th e total funding you receive is $47.50. How much does each friend donate?

53. CRITICAL THINKING A neighbor pays you and two friends $90 to paint her garage. You divide the money three ways in the ratio 2 : 3 : 5.

a. How much does each person receive?

b. What is one possible reason the money is not divided evenly?

h

B = 93.5 in.2

4800 mg



Section 1.2 Solving Multi-Step Equations 11

Solving Multi-Step Solving Multi-Step EquationsEquations1.2

Learning Target: Write and solve multi-step equations.

Success Criteria: • I can apply properties to produce equivalent equations. • I can solve multi-step equations. • I can use multi-step equations to model and solve real-life problems.

Finding Angle Measures

Work with a partner. Find each angle measure in each fi gure. Use equations to justify your answers.

a.

q °

q °3q °

b.

(m + 10)°

2m°

m°

c.

x °(x + 5)°

(x + 10)°

d.

y°(y − 30)°

e.

(t + 5)°

w °

n°

n°

n°

n°y °

m°

m°

p°

p°

p°t °

x °

x ° f °

s°

k °

Find Entry PointsHow do you decide which triangle to solve fi rst? Explain.

Math Practice



1.2 Lesson

Solving Multi-Step EquationsTo solve multi-step equations, use inverse operations to isolate the variable.

Key Idea

Solving a Two-Step EquationEXAMPLE 1

Solve 3x + 15 = 24.

3x + 15 = 24 Write the equation.


3x = 9 Simplify.

3x

— 3

= 9

— 3


x = 3 Simplify.



1. 2z − 1 = −5 2. −3z + 1 = 7 3. 1 — 2

x − 9 = −25

Solving a Multi-Step EquationEXAMPLE 2

Solve 8x − 6x − 25 = −35.

8x − 6x − 25 = −35 Write the equation.

2x − 25 = −35 Combine like terms.

+ 25 + 25 Addition Property of Equality

2x = −10 Simplify.

2x

— 2

= −10

— 2


x = −5 Simplify.

Th e solution is x = −5.


4. −4n − 8n + 17 = 23 5. 10 = 3n + 20 − n

Undo the addition.




Check

3x + 15 = 24

3(3) + 15 =? 24

24 = 24 ✓






8. −5x + 1 = 31 9. 1 — 3

x − 9 = −12

10. −n − 6n + 4 = 53 11. 14 = 6n + 6 − 2n

12. −8(x + 1) + 2x = −32 13. 3 + 4.5(2d − 3) = 7.5

14. WRITING Write the sentence as an equation, then solve.

2 more than 3 times a number x is 17.

15. OPEN-ENDED Explain how to solve the equation 2(4x − 11) + 9 = 19.

16. CRITICAL THINKING How can you solve 3(x + 2) = 9 without distributing the 3?

Using the Distributive Property to Solve an EquationEXAMPLE 3

Solve 2(1 − 5x) + 4 = −8.

2(1 − 5x) + 4 = −8 Write the equation.

2(1) − 2(5x) + 4 = −8 Distributive Property

2 − 10x + 4 = −8 Multiply.

−10x + 6 = −8 Combine like terms.


−10x = −14 Simplify.

−10x

— −10

= −14

— −10


x = 1.4 Simplify.

Th e solution is x = 1.4.


6. −3(x + 2) + 5x = −9 7. 5 + 1.5(2d − 1) = 0.5

Another Method

2(1 − 5x) + 4 = −8

2(1 − 5x) = −12

1 − 5x = −6

−5x = −7

x = 1.4 ✓




17. Find the number x of action fi gures that a small business needs to produce on Friday so that the mean number of action fi gures produced per day is 50.

18. DIG DEEPER A hard drive is 80% full and has 12,000 MB of free space. One minute of video uses 60 MB of storage. How many minutes of video should be deleted so that the hard drive is 75% full?

19. A teacher spends $354 on costumes and microphones for six cast members in a play. Each cast member receives a costume that costs $38 and a microphone that costs $c. What did the teacher spend on each microphone? Justify your answer.

Find the number x of miles you need to run on Friday so that the mean number of miles run per day is 1.5.

You are given the number of miles you run each day from Monday through Th ursday. You are asked how many miles you need to run on Friday so that your daily average for the fi ve days is 1.5 miles.

Write and solve an equation using the defi nition of mean.

2 + 0 + 1.5 + 0 + x

—— 5

= 1.5 sum of the data

—— number of values

= mean

3.5 + x

— 5

= 1.5 Combine like terms.

5 ⋅ 3.5 + x

— 5

= 5 ⋅ 1.5 Multiplication Property of Equality

3.5 + x = 7.5 Simplify.

− 3.5 − 3.5 Subtraction Property of Equality

x = 4 Simplify.

So, you need to run 4 miles on Friday.

EXAMPLE 4 Modeling Real Life

Understandthe problem.

Make a plan.

Solve and check.

Check You run 2 + 1.5 + 4 = 7.5 miles in 5 days. So, the mean number of miles run per day

is 7.5

— 5

= 1.5. ✓

Day Miles

Monday 2

Tuesday 0

Wednesday 1.5

Th ursday 0

Friday x

DayAction Figures

Monday 55

Tuesday 45

Wednesday 53

Th ursday 44

Friday x

y




1.2 Practice

Review & RefreshSolve the equation.

1. y + 8 = 3 2. h − 1 = 7.2

3. 5 = −2n 4. −3.3m = −1.1

Write the decimal as a fraction or mixed number in simplest form.

5. −0.2 6. 3.82 7. −0.454 8. −0.125

Concepts, Skills, & Problem SolvingFINDING ANGLE MEASURES Find each angle measure in the fi gure. Use equations to justify your answers. (See Exploration 1, p. 11.)

9. 4y°

20°(y − 10)°

10.

x° 2x°

(x + 30)°


11. 10x + 2 = 32 12. 19 − 4c = 17

13. 5x + 2x + 4 = 18 14. 2 = −9n + 22 − n

15. 1.1x + 1.2x − 5.4 = −10 16. 2

— 3

h − 1

— 3

h + 11 = 8

17. 6(5 − 8v) + 12 = −54 18. 21(2 − x) + 12x = 44

19. 8.5 = 6.5(2d − 3) + d 20. − 1

— 4

(x + 2) + 5 = −x

YOU BE THE TEACHERYOU BE THE TEACHER Your friend solves the equation. Is your friend correct? Explain your reasoning.

21.

−2(7 − y) + 4 = −4 −14 − 2y + 4 = −4 −10 − 2y = −4 −2y = 6 y = −3

22.

3(y − 1) + 8 = 11 3y − 3 + 8 = 11 3y + 5 = 11 3y = 6 y = 2

23. STRUCTURE Th e cost C (in dollars) of making n watches is represented by C = 15n + 85. How many watches are made when the cost is $385?



24. MODELING REAL LIFE Th e height of the house is 26 feet. What is the height x of each story?

25. MODELING REAL LIFE After the addition of an acid, a solution has a volume of 90 milliliters. Th e volume of the solution is 3 milliliters greater than 3 times the volume of the solution before the acid was added. What was the original volume of the solution?

26. PROBLEM SOLVING A grocer prepares free samples of a salad to give out during the day. By lunchtime, the grocer has given out 5 fewer than half the total number of samples. How many samples did the grocer prepare if she gives out 50 samples before lunch?

27. GEOMETRY What is the length of the missing base of the trapezoid?

28. MODELING REAL LIFE You order two servings of pancakes and a fruit cup. Th e cost of the fruit cup is $1.50. You leave a 15% tip. Your total bill is $11.50. How much does one serving of pancakes cost?

29. PROBLEM SOLVING How many people must attend the third show so that the average attendance per show is 3000?

30. DIG DEEPER Divers in a competition are scored by an international panel of judges. Th e highest and the lowest scores are dropped. Th e total of the remaining scores is multiplied by the degree of diffi culty of the dive. Th is product is multiplied by 0.6 to determine the fi nal score.

a. A diver’s fi nal score is 77.7. What is the degree of diffi culty of the dive?

b. CRITICAL THINKING Th e degree of diffi culty of a dive is 4.0.

Th e diver’s fi nal score is 97.2. Judges award half or whole points from 0 to 10. What scores could the judges have given the diver?

Judge Russia China Mexico Germany Italy Japan Brazil

Score 7.5 8.0 6.5 8.5 7.0 7.5 7.0

6 ft

x

x

Area = 21 in.2

8 in.

3 in.

Theater Attendance

700

1400

2100

2800

3500

4200

0

Show

Att

end

ance

321

25802920

?



Section 1.3 Solving Equations with Variables on Both Sides 17

Solving Equations with Solving Equations with Variables on Both SidesVariables on Both Sides1.3

Learning Target: Write and solve equations with variables on both sides.

Success Criteria: • I can explain how to solve an equation with variables on both sides. • I can determine whether an equation has one solution, no solution, or infi nitely

many solutions. • I can use equations with variables on both sides to model and solve real-life problems.

Finding Missing Measures in Figures


a. If possible, fi nd the value of x so that the value of the perimeter (in feet) is equal to the value of the area (in square feet) for each fi gure. Use an equation to justify your answer.

3 ft

x ft

x ft

2 ft

x ft

2 ft

1 ft

3 ft

b. If possible, fi nd the value of y so that the value of the surface area (in square inches) is equal to the value of the volume (in cubic inches) for each fi gure. Use an equation to justify your answer.

8 in.4 in.

y in.

4 in.

4 in.

y in.

c. How are the equations you used in parts (a) and (b) diff erent from equations used in previous sections? Explain how to solve this type of equation.

Use OperationsWhat properties do you need to use to solve for x in each fi gure?

Math Practice



1.3 Lesson

Solving Equations with Variables on Both SidesTo solve equations with variables on both sides, collect the variable terms on one side and the constant terms on the other side.

Key Idea

Solving an Equation with Variables on Both SidesEXAMPLE 1

Solve 15 − 2x = −7x. Check your solution.

15 − 2x = −7x Write the equation.

+ 2x + 2x Addition Property of Equality

15 = −5x Simplify.

15

— −5

= −5x

— −5


−3 = x Simplify.

Th e solution is x = −3.


1. −3x = 2x + 20 2. 2.5y + 6 = 4.5y − 1

Using the Distributive Property to Solve an EquationEXAMPLE 2

Solve −2(x − 5) = 6(2 − 0.5x).

−2(x − 5) = 6(2 − 0.5x) Write the equation.

−2x + 10 = 12 − 3x Distributive Property


x + 10 = 12 Simplify.


x = 2 Simplify.



3. 6(4 − z) = 2z 4. 5(w − 2) = −2(1.5w + 5)

Check

15 − 2x = −7x

15 − 2(−3) =? −7(−3)

21 = 21 ✓




Undo the addition.



Solving an Equation with No SolutionEXAMPLE 3

Solve 3 − 4x = −7 − 4x.

3 − 4x = −7 − 4x Write the equation.


3 = − 7 ✗ Simplify.

Th e equation 3 = −7 is never true. So, the equation has no solution.

Try It Solve the equation.

5. 2x + 1 = 2x − 1 6. 6(5 − 2v) = −4(3v + 1)

Some equations do not have one solution. Equations can also have no solution or infi nitely many solutions.

When solving an equation that has no solution, you will obtain an equivalent equation that is not true for any value of the variable, such as 0 = 2.

Solving an Equation with Infi nitely Many SolutionsEXAMPLE 4

Solve 6x + 4 = 4 ( 3 — 2

x + 1 ) .

6x + 4 = 4 ( 3 — 2

x + 1 ) Write the equation.

6x + 4 = 6x + 4 Distributive Property

− 6x − 6x Subtraction Property of Equality

4 = 4 Simplify.

Th e equation 4 = 4 is always true. So, the equation has infi nitely many solutions.

Try It Solve the equation.

7. 1 — 2

(6t − 4) = 3t − 2 8. 1 — 3

(2b + 9) = 2

— 3

( b + 9

— 2

)

When solving an equation that has infi nitely many solutions, you will obtain an equivalent equation that is true for all values of the variable, such as − 5 = − 5.

Check Choose any value of x, such as x = 2.

6x + 4 = 4 ( 3

— 2

x + 1 )

6(2) + 4 =? 4 [ 3

— 2

(2) + 1 ]

12 + 4 =? 4(3 + 1)

16 = 16 ✓






10. OPEN-ENDED Write an equation with variables on both sides that has a single solution of −1. Explain how to solve your equation.

STRUCTURE Without solving, determine whether the equation has one solution, no solution, or infi nitely many solutions. Justify your answer.

11. 3(x − 1) = −3 12. 6x + 6 = 6(x + 1) 13. z + 1 = z + 6

SOLVING AN EQUATION Solve the equation. Check your solution, if possible.

14. −7x = x + 24 15. 8(3 − z) = 4z 16. 2(t − 3) = 2t − 6

17. WRITING AND SOLVING AN EQUATION Th e squares are identical. What is the area of each square?

Writing and Solving an EquationEXAMPLE 5Th e circles are identical. What is the area of each circle?

A. 2 B. 4

C. 16π D. 64π

Th e radius of the green circle is x + 2 and the radius of the

purple circle is 4x

— 2

= 2x. Th e circles are identical, so the

radius of each circle is the same. Write and solve an equation to fi nd the value of x.

x + 2 = 2x Write an equation. The radii are equal.

− x − x Subtraction Property of Equality

2 = x Simplify.

When x = 2, the radius of each circle is 4 and the area of each circle is π r 2 = π (4)2 = 16π.

So, the correct answer is C.

Try It 9. WHAT IF? Th e diameter of the purple circle is 3x. What is the area of

each circle?

x + 2

4x

3x + 7 5x + 1




18. Your cousin renews his apartment lease and pays a new monthly rent. His new rent is calculated by applying a discount of $50 to his original rent and then applying a 10% increase to the discounted amount. What was your cousin’s original monthly rent when his new rent is 5% greater?

19. DIG DEEPER You and your friend race on a trail that is 10 miles long. In each situation, does your friend pass you before the end of the trail? Justify your answer.

a. You have a four-mile head start and jog at 6 miles per hour. Your friend bikes at 8 miles per hour.

b. You have a fi ve-mile head start and run at 7 miles per hour. Your friend bikes at 17 miles per hour.

A boat travels x miles per hour upstream on the Mississippi River. On the return trip, the boat travels 2 miles per hour faster. How far does the boat travel upstream?

Th e boat travels the same distance upstream as on the return trip. Th e speed of the boat on the return trip is (x + 2) miles per hour. Write and solve an equation to fi nd the distance upstream.

Distance upstream Distance of return trip

x(3) = (x + 2)(2.5) Write an equation.

3x = 2.5x + 5 Distributive Property

− 2.5x − 2.5x Subtraction Property of Equality

0.5x = 5 Simplify.

0.5x —

0.5 =

5 —

0.5 Division Property of Equality

x = 10 Simplify.

Th e boat travels 10 miles per hour for 3 hours upstream.

So, the boat travels 10 mi

— 1 h

× 3 h = 30 miles upstream.

Time(hours)

Time(hours)

Rate on return trip(miles per hour)

Rate upstream(miles per hour) = • •

Modeling Real LifeEXAMPLE 6

rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr

55

3

32

3

159

Red Bud

Evansville

ereChesChSte.Genevieve

estereste

3 hours2.5 hours




1.3 Practice

Review & RefreshSolve the equation. Check your solution.

1. −9z + 2 = 11 2. −3n − 4n − 17 = 25

3. −2(x + 3) + 5x = −39 4. −15 + 7.5(2d − 1) = 7.5

Find the volume of the solid.

5.

4.5 cm

3 cm2 cm

6.

2 cm

4.5 cm3.5 cm

7.

B = 18 in.2

4 in.

Concepts, Skills, & Problem SolvingFINDING MISSING MEASURES IN FIGURES If possible, fi nd the value of x so that the value of the surface area (in square inches) is equal to the value of the volume (in cubic inches). Use an equation to justify your answer. (See Exploration 1, p. 17.)

8.

11 in. 3 in.

x in.

9.

9 in. 4 in.

x in.

10.

x in.

3 in.

6 in.


11. m − 4 = 2m 12. 3k − 1 = 7k + 2 13. 6x = 5x + 22

14. −24 − 8p = 4p 15. 12(2w − 3) = 6w 16. 2(n − 3) = 4n + 1

17. 2(4z − 1) = 3(z + 2) 18. 0.1x = 0.2(x + 2) 19. 1

— 6

d + 2

— 3

= 1

— 4

(d − 2)

20. YOU BE THE TEACHERYOU BE THE TEACHER Your friend solves the equation shown. Is your friend correct? Explain your reasoning.

3x − 4 = 2x + 1 3x − 4 − 2x = 2x + 1 − 2x x − 4 = 1 x − 4 + 4 = 1 − 4 x = −3



21. MODELING REAL LIFE Write and solve an equation to fi nd the number of miles you must drive to have the same cost for each of the car rentals.

SOLVING AN EQUATION Solve the equation. Check your solution, if possible.

22. x + 6 = x 23. 3x − 1 = 1 − 3x 24. 3x + 15 = 3(x + 5)

25. 4x − 9 = 3.5x − 9 26. 1

— 3

(9x + 3) = 3x + 1 27. 5x − 7 = 4x − 1

28. 1 — 2

x + 1

— 2

x = x + 1 29. 2x + 4 = −(−7x + 6) 30. 5.5 − x = −4.5 − x

31. −3(2x − 3) = −6x + 9 32. 10x − 8

— 3

− 4x = 6x 33. 6(7x + 7) = 7(6x + 6)

34. YOU BE THE TEACHERYOU BE THE TEACHER Your friend solves the equation shown. Is your friend correct? Explain your reasoning.

35. OPEN-ENDED Write an equation with variables on both sides that has no solution. Explain why it has no solution.

36. MODELING REAL LIFE A cable television provider charges $75 for installation and $39.96 per month for a basic entertainment package. A satellite television provider off ers free installation and charges $13.32 per month for service for each television. Your neighbor subscribes to the cable provider the same month you subscribe to the satellite provider. After how many months is your neighbor’s total cost the same as your total cost when you own three televisions?

37. MODELING REAL LIFE A pizza parlor makes 52 pizza crusts the fi rst week of summer and 180 pizza crusts each subsequent week. A diner makes 26 pizza crusts the fi rst week of summer and 90 pizza crusts each subsequent week. In how many weeks will the total number of pizza crusts made by the pizza parlor be twice the total number of pizza crusts made by the diner?

38. PRECISION Is the triangle an equilateral triangle? Justify your answer.

$20 plus $0.50 per mile $30 plus $0.25 per mile

2x + 6.2

3x + 1.22x + 5.2

−4(2n − 3) = 12 − 8n −8n + 12 = 12 − 8n −8n = −8n 0 = 0

The solution is n = 0.



GEOMETRY Find the perimeter of the regular polygon.

39.

5 − 2x −4x + 9

40.

5x − 6

3(x − 1) 41. x + 7

x −43

13

42. PRECISION Th e cost of mailing a DVD in an envelope using Company Bis equal to the cost of mailing a DVD in a box using Company A. What is the weight of the DVD with its packing material? Round your answer to the nearest hundredth.

43. WRITING Would you solve the equation 0.25x + 7 = 1

— 3

x − 8 using

fractions or decimals? Explain.

44. NUMBER SENSE Th e weight of an object is equal to 3

— 4

of its own weight

plus 3

— 4

of a pound. How much does the object weigh? Explain.

45. STRUCTURE Fill in the blanks in three diff erent ways to create an equation that has one solution, no solution, and infi nitely many solutions.

7x + 3x + 10 = −2 ( x + )

46. MODELING REAL LIFE Th e volume of red blood cells in a blood sample is equal to the total volume of the sample minus the volume of plasma. What is the total volume x of blood drawn?

47. PROBLEM SOLVING One serving of oatmeal provides 16% of the fi ber you need daily. You must get the remaining 21 grams of fi ber from other sources. How many grams of fi ber should you consume daily? Justify your answer.

48. DIG DEEPER Th e fl oor of a six-foot-wide hallway is painted as shown, using equal amounts of white and black paint.

a. How long is the hallway?

b. Can this same hallway be painted with the same pattern, but using twice as much black paint as white paint? Explain.

49. PRECISION Consider the equation c = ax − bx, where a, b, and c are whole numbers. Which of the following result in values of a, b, and c so that the original equation has exactly one solution? Justify your answer.

a − b = 1, c = 0 a = b, c ≠ 0 a = b, c = 0 a ≠ b, c = 0

Packing Material

Company A Company B

Box $2.25 $2.50 per lb $8.50 per lb

Envelope $1.10 $2.50 per lb $8.50 per lb

5.5 mL

x

45%Redbloodcells

Plasma

x

x + 1

x

x + 1

x

x + 1

x

x + 1

6 ft

x



Section 1.4 Rewriting Equations and Formulas 25

EXPLORATIONEXPLORATION

Rewriting Equations Rewriting Equations and Formulasand Formulas1.4

Learning Target: Solve literal equations for given variables and convert temperatures.

Success Criteria: • I can use properties of equality to rewrite literal equations. • I can use a formula to convert temperatures.

Rewriting Formulas


a. Write a formula for the height h of each fi gure. Explain your method.

• A parallelogram with area A and base b

• A rectangular prism with volume V, length ℓ, and width w

• A triangle with area A and base b

b. Write a formula for the length ℓ of each fi gure. Explain your method.

• A rectangle with perimeter P and width w

• A rectangular prism with surface area S, width w, and height h

c. Use your formulas in parts (a) and (b) to fi nd the missing dimension of each fi gure.

b = 8 m

hA = 56 m2

w = 4 in. P = 19 in.

h

A = 10 in.2

b = in.52

S = 108 m2

w = 4 m

h = 3 m

V = 60 in.3

B = 12 in.2

h

Find General MethodsWhen does it make more sense to use the formulas you wrote in part (a) than the original area and volume formulas?

Math Practice



1.4 Lesson

Multi-Language Glossary at BigIdeasMath.com

Rewriting an EquationEXAMPLE 1

Solve the equation 2y + 5x = 6 for y.

2y + 5x = 6 Write the equation.

2y + 5x − 5x = 6 − 5x Subtraction Property of Equality

2y = 6 − 5x Simplify.

2y

— 2

= 6 − 5x

— 2


y = 3 − 5

— 2

x Simplify.

Try It Solve the equation for y.

1. 5y − x = 10 2. 4x − 4y = 1 3. 12 = 6x + 3y

Rewriting a FormulaEXAMPLE 2

Th e formula for the surface area S of a cone is S = 𝛑 r 2 + 𝛑 rℓ. Solve the formula for the slant height ℓ.

S = π r 2 + π rℓ Write the formula.

S − π r 2 = π r 2 − π r 2 + π rℓ Subtraction Property of Equality

S − π r 2 = π rℓ Simplify.

S − π r 2

— π r

= π rℓ —

π r Division Property of Equality

S − π r 2

— π r

= ℓ Simplify.

Try It Solve the formula for the red variable.

4. Area of rectangle: A = bh 5. Simple interest: I = Prt

6. Surface area of cylinder: S = 2π r 2 + 2π r h

An equation that has two or more variables is called a literal equation. To rewrite a literal equation, solve for one variable in terms of the other variable(s).

Undo the addition.


RememberA formula shows how one variable is related to one or more other variables. A formula is a type of literal equation.

Key Vocabulary literal equation, p. 26

r





8. REWRITING A FORMULA Th e formula for the circumference of a circle is C = 2πr . Solve the formula for r.

9. DIFFERENT WORDS, SAME QUESTION Which is diff erent? Find “both” answers.

Rewriting the Temperature FormulaEXAMPLE 3Solve the temperature formula for F.

C = 5

— 9

(F − 32) Write the temperature formula.

9

— 5

⋅ C = 9

— 5

⋅ 5

— 9

(F − 32) Multiplication Property of Equality

9

— 5

C = F − 32 Simplify.

9

— 5

C + 32 = F − 32 + 32 Addition Property of Equality

9

— 5

C + 32 = F Simplify.

Th e rewritten formula is F = 9

— 5

C + 32.

Try It

7. Solve the formula F = 9

— 5

C + 32 for C. Justify your answer.

Temperature ConversionA formula for converting from degrees Fahrenheit F to degrees Celsius C is

C = 5

— 9

(F − 32).

Key Idea

Use the reciprocal.


Solve 4x = 6 + 2y for y. Solve 6 = 4x − 2y for y.

Solve 2y − 4x = −6 for y. Solve 2y − 4x = 6 for y.




10. Room temperature is considered to be 70°F. Th e temperature outside is currently 23°C. Is this greater than or less than room temperature?

11. DIG DEEPER A bird fl ies at a top speed of 20,000 meters per hour. Th e bird fl ies 30,000 meters without stopping.

a. For how many hours did the bird fl y if it fl ew at top speed?

b. In part (a), did you rewrite a formula to fi nd the number of hours the bird fl ew, or did you use another approach? Explain.

12. A ball pit is in the shape of a cylinder with a lateral surface area of 245 square feet. Th e diameter of the ball pit is 312 inches. What is the height of the ball pit? Justify your answer.

Which has the greater temperature?

You are given the temperature of the Sun in degrees Fahrenheit and the temperature of lightning in degrees Celsius. You are asked which temperature is greater.

Convert the Celsius temperature to Fahrenheit. Th en compare the temperatures.

F = 9

— 5

C + 32 Write the rewritten formula from Example 3.

= 9

— 5

(30,000) + 32 Substitute 30,000 for C.

= 54,032 Simplify.

Because 54,032°F > 11,000°F, lightning has the greater temperature.

EXAMPLE 4 Modeling Real Life


Make a plan.

Solve and check.

Another Method Compare the temperatures in degrees Celsius.

When F = 11,000, C = 5

— 9

(F − 32) = 5 — 9

(11,000 – 32) ≈ 6093.

Because 30,000°C > 6093°C, lightning has the greater temperature. ✓

Sun11,000°F

Lightning30,000°C

Th e

a.

b.

12. A b245hei




1.4 Practice

Review & RefreshSolve the equation. Check your solution, if possible.

1. −2x = x + 15 2. 4(z − 3) = 2z

3. x − 8 = x − 1 4. 5(4 + t) = 5t + 20

Find the unit rate.

5. 60 miles in 5 hours 6. $8.50 : 5 ounces 7. 9 pounds per 6 crates

Concepts, Skills, & Problem SolvingREWRITING FORMULAS Solve the formula for the height of the fi gure. Th en use the new formula to fi nd the height. (See Exploration 1, p. 25.)

8. A= 1

— 2

bh 9. V = Bh

A = 36 mm2

h

b = 12 mm

V = 36 in.3

h

B = 6 in.2

IDENTIFYING LITERAL EQUATIONS Is the equation a literal equation? Explain.

10. y = 4 11. t + 8 y = 7 12. z = 4x + 9y

REWRITING AN EQUATION Solve the equation for y.

13. 1

— 3

x + y = 4 14. 3x + 1

— 5

y = 7 15. 6 = 4x + 9y

16. π = 7x − 2y 17. 4.2x − 1.4y = 2.1 18. 6y − 1.5x = 8

19. YOU BE THE TEACHERYOU BE THE TEACHER Your friend rewrites the equation 2x − y = 5. Is your friend correct? Explain your reasoning.

REWRITING A FORMULA Solve the formula for the red variable.

20. d = rt 21. e = mc 2 22. R − C = P

23. P = a + b + c 24. B = 3 V

— h

25. D = m — V

222xx − yy == 555

yy = −222xx +++ 555



26. MODELING REAL LIFE Th e formula K = C + 273.15 converts temperatures from degrees Celsius C to Kelvin K.

a. Convert 200 degrees Celsius to Kelvin.

b. Solve the formula for C.

c. Convert 300 Kelvin to degrees Celsius.

27. PROBLEM SOLVING Th e formula for simple interest is I = Prt.

a. Solve the formula for t, when r is the simple interest per year.

b. Use the new formula to fi nd the value of t in the table.

28. GEOMETRY Use the triangle shown.

a. Write a formula for the perimeter P of the triangle.

b. Solve the formula for b.

c. Use the new formula to fi nd b when a is 10 feet and c is 17 feet.

29. REASONING Th e formula K = 5

— 9

(F − 32) + 273.15 converts

temperatures from degrees Fahrenheit F to Kelvin K.

a. Solve the formula for F.

b. Th e freezing point of helium is 0.95 Kelvin. What is this temperature in degrees Fahrenheit?

c. Th e temperature of dry ice is −78.5°C. Which is colder, dry ice or liquid nitrogen?

30. MODELING REAL LIFE In which city is the water temperature higher?

31. GEOMETRY Th e volume of a square pyramid with a height of 30 feet is 360 cubic feet. What are theside lengths of the base? Justify your answer.

32. DIG DEEPER Th e Navy Pier Ferris Wheel in Chicago has a circumference that is 56% of the circumference of the fi rst Ferris wheel built in 1893.

a. What is the radius of the Navy Pier Ferris Wheel?

b. What was the radius of the fi rst Ferris wheel?

c. Th e fi rst Ferris wheel took 9 minutes to make a complete revolution. How fast was the wheel moving?

bPerimeter = 42 feet

a c

38°FPortland

CURRENT WATER TEMPERATURES

2°CBoston

C = 439.6 ft

I $75

P $500

r 5%

t


Connecting Concepts

Performance Task

oCoCCC

At the beginning of this chapter, you watched a STEAM Video called “Training for a Half Marathon." You are now ready to complete the performance task related to this video, available at BigIdeasMath.com. Be sure to use the problem-solving plan as you work through the performance task.

Target Heart Rates

Connecting Concepts 31

Using the Problem-Solving Plan1. Th e battery life of a one-year-old cell phone is 75% of its original

battery life. When the battery is charged to 50% of its capacity, it

dies after 4 1

— 2

hours. Find the original battery life of the phone. Justify

your answer.

You know how long a cell phone battery lasts when it is charged to 50% of its capacity. You also know that the battery life of the phone is 75% of its original battery life. You are asked to fi nd the original battery life of the phone.

First, fi nd the battery life of the one-year-old cell phone. Th en use this information to write and solve an equation for the original battery life of the phone.

Use the plan to solve the problem. Th en check your solution.

2. Th e triangular prism shown has a volume of 132 cubic centimeters. Find the height of the prism. Justify your answer.


Make a plan.

Solve and check.

Problem-Solving StrategiesUsing an appropriate strategy will help you make sense of problems as you study the mathematics in this course. You can use the following strategies to solve problems that you encounter.● Use a verbal model.● Draw a diagram.● Write an equation.

● Solve a simpler problem.● Sketch a graph or

number line.

● Make a table.● Make a list.● Break the problem into parts.

6 cm 8 cm

h


Review VocabularyWrite the defi nition and give an example of the vocabulary term.

literal equation, p. 26

Graphic OrganizersYou can use an Information Frame to help organize and remember a concept. Here is an example of an Information Frame for solving equations with variables on both sides.

Solving Equations with

Variables on Both Sides

Example:14 + 3x = 4x + 5

–3x –3x 14 = x + 5

–5 –5

9 = x

Procedure: To solve equations with variables on both

sides, collect the variable terms on one

side and the constant terms on

the other side.Words:No solution:

You obtain an

equivalent equation

that is not true for

any value of the

variable, such

as 2 = 4.

Words: Infinitely many

solutions: You

obtain an equivalent

equation that is

true for all values

of the variable,

such as

–1 = –1.

Choose and complete a graphic organizer to help you study the concept.

Chapter Review Go to BigIdeasMath.com to download blank graphic organizers.

1. solving simple equations using addition

2. solving simple equations using subtraction

3. solving simple equations using multiplication

4. solving simple equations using division

5. inverse operations

6. literal equation


C

“I finished my Information Frame about Romulus and Remus. What did Romulus and Remus say to

their mommy?”


Chapter Review 33

Chapter Self-AssessmentAs you complete the exercises, use the scale below to rate your understanding of thesuccess criteria in your journal.

1 2 3 4I can teach

someone else.I do not understand. I can do it

with help.I can do it on

my own.

1.1 Solving Simple Equations (pp. 3–10)

Learning Target: Write and solve one-step equations.

Solve the equation. Check your solution.

1. y + 8 = −11 2. 3.2 = −0.4n 3. − t — 4

= −3π

4. v − ∣ 2.4 ∣ = 5.7 5. −6 = −2 + w 6. x − 2

— 3

= − 11 —

12

7. Th e boiling point of a liquid is the temperature at which

the liquid becomes a gas. Th e boiling point of mercury is

about 41

— 200

of the boiling point of lead. Write and solve an

equation to fi nd the boiling point of lead.

8. Write an equation that you can use the Addition Property of Equality to solve.

9. To solve 2

— 5

x = 14, you multiply both sides of the equation

by 5

— 2

. Your friend divides both sides of the equation by 2

— 5

.

Who is correct? Explain.

10. Write and solve an equation to fi nd the value of x.

55°(x + 10)°

11. Th e circumference C of a circle is 24π inches. Use the formula C = 2πr to fi nd the radius r of the circle.

°C/ °F Lock

MODE

Boiling pointof mercury



Solve the equation. Check your solution.

12. 3n + 12 = 30 13. 2(3 − p) − 17= 41

14. −14x + 28 + 6x = −44 15. 1.06(12.95 + x) = 31.27

16. Th e sum of the angle measures of a quadrilateral is 360°. Find the value of x. Th en fi nd the angle measures of the quadrilateral.

17. Th e equation P = 2.5m + 35 represents the price P (in dollars) of a bracelet, where m is the cost of the materials (in dollars). Th e price of a bracelet is $115. What is the cost of the materials?

18. A 455-foot fence encloses a pasture. What is the length of each side of the pasture?

Learning Target: Write and solve multi-step equations.

1.2 Solving Multi-Step Equations (pp. 11–16)

x °12

x °

x ° x °

12

180 ft

x ft1.5x ft

3x ft

Solve the equation. Check your solution, if possible.

19. 3(x − 4) = −2(4 − x) 20. 4 − 5k = −8 − 5k

21. 5m − 1 = 4m + 5 22. 3(5p − 3) = 5(p − 1)

23. 0.4n + 0.1 = 0.5(n + 4) 24. 7t + 3 = 8 + 7t

25. 1

— 5

(15b − 7) = 3b − 9 26. 1

— 6

(12z − 18) = 2z − 3

27. Th e side lengths of an isosceles triangle are (3x + 1) inches, (4x + 5) inches, and (2x + 7) inches. Find the perimeters of two possible triangles.

Learning Target: Write and solve equations with variables on both sides.

1.3 Solving Equations with Variables on Both Sides (pp. 17–24)


Chapter Review 35

28. A shuttle company charges $3.25 plus $0.55 per mile. A taxi company charges $2.50 plus $0.60 per mile. After how many miles will both companies charge the same amount?

29. You begin the year with $25 in a savings account and $50 in a checking account. Each week you deposit $5 into the savings account and $10 into the checking account. In how many weeks is the amount in the checking account twice the amount in the savings account?

Learning Target: Solve literal equations for given variables and convert temperatures.

1.4 Rewriting Equations and Formulas (pp. 25–30)

Solve the equation for y.

30. 6y + x = 8 31. 10x − 1 — 3

y = 15 32. 20 = 5x + 10y

33. Th e formula F = 9

— 5

(K − 273.15) + 32 converts a temperature from

Kelvin K to Fahrenheit F.

a. Solve the formula for K.

b. Convert 240°F to Kelvin. Round your answer to the nearest hundredth.

34. Use the trapezoid shown.

a. Write the formula for the area A of a trapezoid.

b. Solve the formula for h.

c. Use the new formula to fi nd the height h of the trapezoid.

35. Th e equation for a line in slope-intercept form is y = mx + b. Solve the equation for x.

36. Th e formula for the volume of a cylinder is V = πr 2h, where r is the radius of the circular base and h is the height of the cylinder.

a. Solve the formula for h.

b. Use the new formula to fi nd the height of the cylinder.

h

8 cm

16 cm

A = 72 cm2

h

1.25 in.

Volume = 6 in.3π



Practice Test

Solve the equation. Check your solution, if possible.

1. 4 + y = 9.5 2. − x

— 9

= −8 3. z − 2

— 3

= 1

— 8

4. 15 = 9 − 3a 5. 4(b + 5) − 9 = −7 6. 9j − 8 = 8 + 9j

7. 3.8n − 13 = 1.4n + 5 8. 9(8d − 5) + 13 = 12d − 2 9. 1

— 4

t + 4 = 3

— 4

(t + 8)

10. Th e sum of the angle measures of a triangle is 180°. Find the value of x. Th en fi nd the angle measures of the triangle.

11. A formula for the perimeter of a rectangle is P = 2ℓ + 2w.

a. Solve the formula for w.

b. Use the new formula to fi nd the width w (in meters) of a rectangle with a perimeter of 2 meters and a length of 40 centimeters.

12. Solve 0.5 = 0.4y − 0.25x for y.

13. Your basketball team wins a game by 13 points. Th e opposing team scores 72 points. Explain how to fi nd your team’s score.

14. You are biking at a speed of 18 miles per hour. You are 3 miles behind your friend, who is biking at a speed of 12 miles per hour. Write and solve an equation to fi nd the amount of time it takes for you to catch up to your friend.

15. Two scientists are measuring the temperatures of lava. One scientist records a temperature of 1725°F. Th e other scientist records a temperature of 950°C. Which is the greater temperature?

16. Your profi t for mowing lawns this week is $24. You are paid $8 per hour and you paid $40 for gas for the lawn mower. How many hours did you work this week?

x ° (x + 8)°

2x °

haapter 1 Equations


Cumulative Practice 37

Cumulative PracticeTest-Taking StrategySolve Directly or Eliminate Choices

1. Which value of x makes the equation true?

4x = 32

A. 8 B. 28

C. 36 D. 128

2. A taxi ride costs $3 plus $2 for each mile driven. You spend $39 on a taxi. Th is can be modeled by the equation 2m + 3 = 39, where m represents the number of miles driven. How long was your taxi ride?

F. 18 mi G. 21 mi

H. 34 mi I. 72 mi

3. Which of the following equations has exactly one solution?

A. 2

— 3

(x + 6) = 2

— 3

x + 4 B. 3

— 7

y + 13 = 13 − 3

— 7

y

C. 4

— 5

( n + 1

— 3

) = 4

— 5

n + 1

— 3

D. 7

— 8

( 2t + 1

— 8

) = 7

— 4

t

4. Th e perimeter of the square is equal to the perimeter of the triangle. What are the side lengths of the square?

3x + 3 2x + 4

7x − 27x − 2

5. Th e formula d = rt relates distance, rate, and time. Solve the formula for t .

F. t = dr G. t = d

— r

H. t = d − r I. t = r —

d

“You can eliminate A and D. Then, solve directly to determine that

the correct answer is B.”



6. What is a possible fi rst step to solve the equation 3x + 5 = 2(x + 7)?

A. Combine 3x and 5. B. Multiply x by 2 and 7 by 2.

C. Subtract x from 3x. D. Subtract 5 from 7.

7. You work as a sales representative. You earn $400 per week plus 5% of your total sales for the week.

Part A Last week, you had total sales of $5000. Find your total earnings. Show your work.

Part B One week, you earned $1350. Let s represent your total sales that week. Write an equation that you can use to fi nd s.

Part C Using your equation from Part B, fi nd s. Show all steps clearly.

8. In 10 years, your aunt will be 39 years old. Let m represent your aunt’s age today. Which equation can you use to fi nd m?

F. m = 39 + 10 G. m − 10 = 39

H. m + 10 = 39 I. 10m = 39

9. Which value of y makes the equation 3y + 8 = 7y + 11 true?

A. −4.75 B. −0.75

C. 0.75 D. 4.75

10. What is the value of x ?

F. 23

G. 39

H. 58

I. 68

ThinkThThThThThiinininkkkkkThinkSolveSSSoSoSoSoSoSolllvlvlvlvlvlveeeeeeSolve

ExExExplplplppp aiaiainnnEEEEEExExExExEx llllplplplplpl iiiiaiaiaiaiainnnnn Explain

32°

(2x + 12)°


Cumulative Practice 39

11. You have already saved $35 for a new cell phone. You need $175 to buy the cell phone. You think you can save $10 per week. At this rate, how many more weeks will you need to save money before you can buy the new cell phone?

12. What is the greatest angle measure in the triangle?

Sum of anglemeasures: 180°

3x °

2x °50°

A. 26° B. 78°

C. 108° D. 138°

13. Which value of x makes the equation 6(x − 3) = 4x − 7 true?

F. −5.5 G. −2

H. 1.1 I. 5.5

14. Th e drawing below shows equal weights on two sides of a balance scale.

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 2000 20 30 40

What can you conclude from the drawing?

A. A mug weighs one-third as much as a trophy.

B. A mug weighs one-half as much as a trophy.

C. A mug weighs twice as much as a trophy.

D. A mug weighs three times as much as a trophy.


solving simple equations

Documents