1. 8-2 Finding Percents Warm Up Problem of the Day Lesson Presentation
Pre-Algebra

2. 8-2 Finding Percents Warm Up Pssa Tested
Pre-Algebra
8-2
Finding Percents
Warm Up Pssa Tested
Rewrite each value as indicated.
1. as a percent
2. 25% as a fraction
as a decimal
as a fraction 24 50
48% 1 4 3 8
0.375 4 25

3. objective for today
Learn to find percents.

4. Finding the Percent One Number Is of Another
What percent of 220 is 88?

5. Finding the Percent One Number Is of Another
What percent of 19 is 95?

6. Finding the Percent One Number Is of Another
18 is what percent of 60?

8. Practice Problems! What percent of 102 is 17?
13 is what percent of 52?

9. Finding the Percent One Number Is of Another
Eddie weighs 160 lb, and his bones weigh 24 lb. Find the percent of his weight that his bones are.
Method 2: Set up a proportion to find the percent.
Think: What number is to 100 as 24 is to 160? =
number
100
part
whole
Set up a proportion. n
100 24
160 =
Substitute.
n  160 = 100  24
Find the cross products.
160n = 2400

10. Additional Example 1 Continued
160
2400
n =
Solve for n.
n = 15 = 15
100 24
160
The proportion is reasonable.
So 15% of Eddie’s weight is bone.

11. Try This: Example 1B
B. Jamie weighs 140 lb, and his bones weigh 21 lb. Find the percent of his weight that his bones are.
Method 2: Set up a proportion to find the percent.
Think: What number is to 100 as 21 is to 140? =
number
100
part
whole
Set up a proportion. n
100 21
140 =
Substitute.
n  140 = 100  21
Find the cross products.
140n = 2100

12. 140
2100
n =
Solve for n.
n = 15 = 15
100 21
140
The proportion is reasonable.
So 15% of Jamie’s weight is bone.

13. Additional Example 2A: Finding a Percent of a Number
A. After a drought, a reservoir had only % of the average amount of water. If the average amount of water is 57,000,000 gallons, how much water was in the reservoir after the drought? 2 3
Choose a method: Set up an equation.
Think: What number is % of 57,000,000? 2 3
w = 66 %  57,000, Set up an equation. 2 3
w =  57,000, % is equivalent to . 2 3

14. Additional Example 2A Continued
w = = 38,000,000
114,000,000 3
The reservoir contained 38,000,000 gallons of water after the drought.

15. Additional Example 2B: Finding Percents
B. Ms. Chang deposited $550 in the bank. Four years later her account held 110% of the original amount. How much money did Ms. Chang have in the bank at the end of the four years?
Choose a method: Set up a proportion. =
110
100 a
550
Set up a proportion.
110  550 = 100  a Find the cross products.
60,500 = 100a

16. Additional Example 2B Continued
605 = a Solve for a.
Ms. Chang had $605 in the bank at the end of the four years.

17. Try This: Example 2B
B. Mr. Downing deposited $770 in the bank. Four years later his account held 120% of the original amount. How much money did Mr. Downing have in the bank at the end of the four years?
Choose a method: Set up a proportion. =
120
100 a
770
Set up a proportion.
120  770 = 100  a Find the cross products.
92,400 = 100a

18. Try This: Example 2B Continued
924 = a Solve for a.
Mr. Downing had $924 in the bank at the end of the four years.

19. Let's Review! 90 is what percent of 75? What percent of 4 is 6?

20. Lesson Quiz
Find each percent to the nearest tenth.
1. What percent of 33 is 22?
2. What percent of 300 is 120?
3. 18 is what percent of 25?
4. The volume of Lake Superior is 2900 mi3 and the volume of Lake Erie is 116 mi3. What percent of the volume of Lake Superior is the volume of Lake Erie?
66.7%
40%
72% 4%

21. Question Time
Help!

22. Learned to find percents.
What we learned today!
Learned to find percents.

23. Complete page 407 in your text
Assignment
Complete page 407 in your text