Variables and Expressions

1.3

Vocabulary

Algebra:Branch of mathematics that uses

symbols such as variables

Variable:A letter or symbol used to

represent an unknown value.Example: x, y

Vocabulary

Algebraic Expression:An expression containing at least

one variable and at least one operation.

Example: 4-x, 5m +6, ab

Defining a Variable:Choosing a variable to represent

an unknown quantity

Translate each phrase into an algebraic expression1. Identify key word for the

operation2. Define your variable3. Translate from left to right

Key Words for OperationsAdd More than; sum of; greater than;

added to; increased by, Subtract Less than; fewer than; subtracted

from; minus; difference of; decreased byMultiply Times; product of; multiplied by

Divide Divided by; quotient of;

Order is always left to right EXCEPT words with “than”

Ex 1: Three dollars more than the cost of a sandwich1. more than : add and switch

order2. C= cost of sandwich3. 3+c but need to switch order

because of the word than!! Answer: C+3

Ex 2: Five points more than the points scored by field goals if each field goal is worth 3 points.

1. More than: add and switch order Each goal is worth 3 points: multiply by 3

2. f= field goals3. 5+3f but because it says the

word than switch the order. Answer: 3f +5

Substitution Property of EqualityIf two quantities are equal, then

one can be replaced by the other.

Evaluate: if x=3, y=4, z=7

Ex 3: 6y-4x Ex 4: 5z+(x+4y)-156(4) 4(3)

24 12

12

5(7) [3 4(4)] 15

5(7) [3 16] 15

5(7) 19 15

35 19 15

54 1539

Evaluate: if x=3, y=4, z=7

Ex 5:( )z x

y

(7 3)

4

(7 3) 4

4 41

Example 6:Suzanne Middle School sold tickets

for a school play. The price of an adult ticket was $3, and the price of a student ticket was $1.

a. Write an expression for the total amount of money collected.

b. Suppose 70 adult tickets and 85 student tickets were sold. How much was collected?

3 1a s

$295

HomeworkPage 16-15 (12-37, 39, 40)