how do you compute successive percents ?
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How do you compute successive percents ?. For example: Eli bought a computer that was on sale for 30% off its original price of $500. Eli also used a coupon for a 15% discount on the sale price. The tax rate was 7.25%. How much did Eli pay for the computer?. - PowerPoint PPT PresentationTRANSCRIPT
How do you compute successive percents?
For example:Eli bought a computer that was on sale for 30% off its original price of $500. Eli also used a coupon for a 15% discount
on the sale price. The tax rate was 7.25%. How much did Eli pay for the
computer?
In this lesson you will learn how to compute successive
percentages by using proportions and equations.
Let’s ReviewUsing Equations
Percent as Decimal x Amount
50% = 0.5
0.5 x 300=150
Let’s Review
Between Ratios
100 x 3 = 30050 x 3 = 150
Within Ratios 50 x 2 = 100
150 x 2 = 300
Proportions Have Equal…
Let’s Review
Proportions Also Have Equal Cross Products
100v = 1,500v = 150
A Common MistakeTotal Percent Change = Sum of Percent Changes
25% off sale, 10% off sale price coupon, 8% Tax
-25% + -10% + 8% = -27% 25% off Original Price = Sale Price
10% off Sale Price = Coupon Price8% more than Coupon Price = Final price
A Common Mistake
Percent Increase(Add Amt Change)
Percent Decrease(Subtract Amt
Change)Tax SaleTip Discount
Markup Coupon
Add or Subtract?
Core LessonEli bought a computer that was on sale for 30%
off its original price of $500. Eli also used a coupon for a 15% discount on the sale price. The tax rate was 7.25%. How much did Eli pay for the
computer?
Core Lesson
Using Between Ratios Using Within Ratios
Core LessonUsing Cross Products
100x = 1,500
x = $150
Core LessonUsing Equations
500 x 0.3 = $150
Core LessonOriginal-(Original x %off) = Sale Price
500-(500x0.3) = 500-150 = $350
500 x (1—0.3) = 500 x 0.7 = $350
30% off is the same as 70% of original amount
Core Lesson15% coupon off of $350
350 – (350 x 0.15) = 350 – 52.50 = $297.50
350 x (1—0.15) = 350 x 0.85 = $297.50
Core Lesson$297.50 plus 7.25% Tax
297.50+(297.50x0.0725)=297.50+21.57=
$319.07297.50 x (1 + 0.0725)= 297.50 x 1.0725 =
$319.07
Adding 7.25% is the same as 107.25% of the original amount
Core Lesson-35% + -15% + 7.25% = -42.75%
500 – (500 x .4275) = 500 – 213.75 = 286.25
35% off Original Price = Sale Price15% off Sale Price = Coupon Price
7.25% more than Coupon Price = Final price
$286.25 versus $319.07
In this lesson you have learned how to calculate successive
percentages by using a proportions and equations.
Guided PracticeAfter eating at your favorite restaurant, you know the bill before tax is $52.60 and the sales tax is 8%. You decide to leave a 20% tip for the waiter based on the pre-tax amount. How much should you leave for the waiter? How much will the bill be with tax? How much will you spend in total?
Extension ActivitiesTom has raised $2,000 and started a charity to provide book bags of school supplies for poor children. Tom packs each bag with 2 notebooks and 10 pencils. At the store the original price of 1 book bag is $22.50, of 1 notebooks is $3.25, and of 1 pencil is $0.19. However, all items are on sale for 30%. Tom also receives an additional 10% discount off of the sale price, because the products are for a charity. Tax is 8.25%. How many book bags can Tom make?
Extension ActivitiesPretend that you deposited $500 in 3 different savings accounts at three banks. Bank A provides customers with 2% interest on their investments per month. Bank B provides 5% and Bank C offers 7%. Create a table of how much money that you will have in each account at the end of each month. How do the amounts compare after 1 year? What about after 5 years?
Extension ActivitiesPretend that had a job that earned 5% commission of your sales. How much would you need to sell to earn one million dollars pre-tax? Your state government deducts 12% from your earnings. The federal government deducts 6.5% from your earnings. How much would you need to sell to earn one million dollars post-tax?
Quick QuizJoe’s bill at the restaurant was $52.70. He decided to leave his server 15% tip on the pre-tax bill. The tax rate is 8%. How much of a tip will he leave? How much is the bill after tax? How much will he spend in total?
A $750 computer is on sale for 25% off. You also have a coupon for 10% off the sale price. Tax is 8%. How much will the computer cost?