1. Splash Screen

2. Solve percent problems using percent equations.
You have already used the percent proportion to solve problems. (Lesson 7–3)
Solve percent problems using percent equations.
Apply the percent equation to real-world problems.
Then/Now

3. Find the Part
Find 38% of 22.
Estimate 40% of 20 is 8.
Example 1

4. n = 0.38 • 22 Write the percent equation.
Find the Part
n = 0.38 • 22 Write the percent equation.
= Multiply.
Answer: 38% of 22 is 8.36.
Check for Reasonableness 8.36 ≈ 8 
Example 1

5. Find 64% of 48.
A. 32
B. 75 C
D. 30
Example 1

6. The whole is 25 and the part is 19. Let n represent the percent.
Find the Percent
19 is what percent of 25?
Estimate
The whole is 25 and the part is 19. Let n represent the percent.
Write the percent equation.
Divide each side by 25.
Example 2

7. Check for Reasonableness 76% ≈ 80% 
Find the Percent
0.76 = n Simplify.
By definition, the percent is expressed as a decimal. Convert 0.76 to a percent.
Answer: 19 is 76% of 25.
Check for Reasonableness 76% ≈ 80% 
Example 2

8. 8 is what percent of 25?
A. 312% B.
C. 32%
D. 2%
Example 2

9. The part is 84 and the percent is 16%. Let n represent the whole.
Find the Whole
84 is 16% of what number?
84 is 16% of what number?
Estimate 80 is 16% of 500.
The part is 84 and the percent is 16%. Let n represent the whole.
Write 16% as the decimal 0.16.
Divide each side by 0.16.
Example 3

10. Check for Reasonableness 525 ≈ 500 
Find the Whole
525 = n Simplify.
Answer: So, 84 is 16% of 525.
Check for Reasonableness 525 ≈ 500 
Example 3

11. 315 is 42% of what number?
A. 750 B C
D. 150
Example 3

12. Concept

13. Method 1 Find the tax first. Then add.
Use the Percent Equation
SALES TAX Chan wants to buy a cell phone that costs $180. If a 7% sales tax is added, what is the total cost?
Method 1 Find the tax first. Then add.
The whole is $180. The percent is 7%. You need to find the amount of the tax, or the part. Let t represent the amount of tax.
t = 0.07 ● 180 Write 7% as a decimal.
t = Multiply.
The tax is $ The total cost is $180 + $12.60 or $
Example 4

14. Method 2 Find the total percent first.
Use the Percent Equation
Method 2 Find the total percent first.
Find 100% + 7% or 107% of $180 to find the total cost, including tax.
t = 1.07 ● 180 Write 107% as a decimal.
t = Multiply.
Answer: Using either method, the total cost is $
Example 4

15. The sales tax on a bicycle is 5%
The sales tax on a bicycle is 5%. If the price of the bicycle is $126, what is the total cost?
A. $126.05
B. $132.30
C. $138.60
D. $163.00
Example 4

16. You are asked to find the estimated percent of sales tax.
Mr. Wilkins purchased a DVD player for $97.19 including tax. The DVD player had a sticker price of $ About what percent sales tax did he pay?
A 6% B 7%
C 8% D 9%
Read the Test Item
You are asked to find the estimated percent of sales tax.
Example 5

17. 7.20 = p ● 89.99 Write the percent equation.
Solve the Test Item
The tax is $97.19 – $89.99 or $7.20.
7.20 = p ● Write the percent equation.
Divide each side by
0.08  p Simplify.
0.08 = 8%
Answer: The correct answer is C.
Example 5

18. Jeanne bought a DVD for $18. 18 including tax
Jeanne bought a DVD for $18.18 including tax. The sticker price of the DVD was $ About what percent sales tax did she pay?
A. 5%
B. 6%
C. 7%
D. 8%
Example 5

19. End of the Lesson