1. Preview
Warm Up
California Standards
Lesson Presentation

2. Warm Up
Solve.
1. 4x = 90
2. 8x = 96
3. 12x = 180
4. 26x = 182
22.5 12 15 7

3. California
Standards
Number Sense (NS1.4) - Calculate given percentages of quantities and solve problems involving discounts at sales, interest earned, and tips.
Also covered: NS1.3, AF1.1

4. Objective: You will learn how to solve problems involving percents.4

5. Sloths sleep an average of 16. 5 hours a day
Sloths sleep an average of 16.5 hours a day. To find out what percent of a 24-hour day 16.5 hours is, you can use a proportion or an equation.

6. Sloths spend about 69% of the day sleeping!
Sloths sleep an average of 16.5 hours a day. To find out what percent of a 24-hour day 16.5 hours is, you can use a proportion or an equation.
Proportion Method
Part n
16.5
Part =
Whole
100 24
Whole
n • 24 = 100 • 16.5
24n = 1,650
n = 68.75
Sloths spend about 69% of the day sleeping!

7. Example 1: Using Proportions to Solve Problems with Percents
A. What percent of 40 is 25?

8. Example 2: Using Proportions to Solve Problems with Percents
B. 15 is 25% of what number?

9. Check It Out! Example 3
Solve.
A. What percent of 50 is 10?

10. Check It Out! Example 4
Solve.
B. 8 is 40% of what number?

11. Helpful Hint
The sales tax rate is the percent used to calculate sales tax.
Sales tax is an amount you pay in addition to the price of the item.

12. Example 5: Finding Sales Tax
A portable DVD player costs $225 before tax at an appliance warehouse. What is the sales tax rate if the tax is $18?
Restate the question: What percent of $225 is $18?

13. Check It Out! Example 6
A new flat screen TV costs $800 before tax at an appliance warehouse. What is the sales tax rate if the tax is $56?
Restate the question: What percent of $800 is $56?

14. Check It Out! Example 7
Joshua buys a sweater that has a sale price of $48. Joshua gives the sales clerk $60 and receives $7.80 in change. What is the sales tax rate?

15. Home Learning
On-Line Tutoring 15

16. Sloths spend about 69% of the day sleeping!
Sloths sleep an average of 16.5 hours a day. To find out what percent of a 24-hour day 16.5 hours is, you can use a proportion or an equation.
Equation Method
What percent of 24 is 16.5?
n • 24 = 16.5 24 24
n =
n = 68.75%
Sloths spend about 69% of the day sleeping!

17. Example 6: Using Equations to Solve Problems with Percents
A. 35 is 28% of what number?
35 = 28% • n
Write an equation.
Write 28% as a decimal.
35 = 0.28 • n 35
0.28
0.28 • n
0.28 =
Divide each side by 0.28.
125 = n
35 is 28% of 125.

18. Example 7: Using Equations to Solve Problems with Percents
B. What percent of 9 is 18?
n • 9 = 18
Write an equation.
n • 9 9 18 9
Divide each side by 9. =
n = 2
Write the decimal as a percent.
n = = 200. = 200%
18 is 200% of 9.

19. Check It Out! Example 8 Solve. A. 36 is 24% of what number?
Write an equation.
Write 24% as a decimal.
36 = 0.24 • n 36
0.24 =
0.24 • n
Divide each side by 0.24.
150 = n
36 is 24% of 150.

20. Check It Out! Example 9 Solve. B. What percent of 6 is 36? n • 6 = 36
Write an equation.
n • 6 6 36 6
Divide each side by 6. =
Write the decimal as a percent.
n = 6
n = = 600. = 600%
n = 600%
36 is 600% of 6.

21. Home Learning
On-Line Tutoring 21

22. Lesson Quiz
Solve.
1. 21 is 42% of what number?
2. What percent of 292 is 73?
3. 112% of what number is 84?
4. What percent of 1,340 is 13.4?
5. An ad features a bicycle on sale for $139. If the total cost of the bike is $147.34, what is the sales tax rate? 50
25% 75 1% 6%