1. Warm Up
Problem of the Day
Lesson Presentation
Lesson Quizzes

2. Write each decimal as a percent and fraction.
Warm Up
Write each decimal as a percent and fraction.
3. 0.2 19 50 __
38%, 3 50 __
6%, 1 5 __
20%,

3. Problem of the Day
Lucky Jim won $16,000,000 in a lottery. Every year for 10 years he spent 50% of what was left. How much did Lucky Jim have after 10 years?
$15,625

4. Learn to find the missing value in a percent problem.

5. To find the percent one number is of another, use this proportion:
% 100 =
is of
Because you are looking for 45% of 420, 45 replaces the percent sign and 420 replaces “of.” The first denominator, 100, always stays the same. The “is” part is what you have been asked to find.

6. Additional Example 1: Application
There are 560 students in Ella’s school. If 35% of the students participate in after-school sports, how many students participate in after- school sports?
First estimate your answer. Think: 35% = ,
which is close to , and 560 is close to 600. So
about of the students participate in after-school sports. 35
100
___ 1 3 __ 1 3 __
• 600 = 200
This is the estimate.
Helpful Hint
Think: “35 out of 100 is how many out of 560?”

7. Additional Example 1 Continued
Now solve:
Let s represent the number of students who participate in after- school sports. 35
100
___ s
560
___ =
100 • s = 35 • 560
The cross products are equal.
100s = 19,600
s is multiplied by 100.
100s
100
____
19,600
100
_____
Divide both sides of the equation by 100 to undo multiplication. =
s = 196
Since 196 is close to your estimate of 200, 196 is a reasonable answer.
196 students participate in after-school sports.

8. Check It Out: Example 1
There are 480 students in Tisha’s school. If 70% of the students participate in the fundraising program, how many students participate in the fundraising program?
First estimate your answer. Think: 70% = ,
which is close to , and 480 is close to 500. So
about of the students participate in after
school sports. 70
100
___ 3 4 __ 3 4 __
• 500 = 375
This is the estimate.

9. Check It Out: Example 1 Continued
Now solve:
Let s represent the number of students who participate in the fundraising program. 70
100
___ s
480
___ =
100 • s = 70 • 480
The cross products are equal.
100s = 33,600
s is multiplied by 100.
100s
100
____
33,600
100
_____
Divide both sides of the equation by 100 to undo multiplication. =
s = 336
Since 336 is close to your estimate of 375, 336 is a reasonable answer.
336 students participate in the fundraising program.

10. Additional Example 2: Application
Johan is 25% of the way through his exercises. If he has exercised for 20 minutes so far, how much longer does he have to work out?
25% of the exercises are completed, so 20 minutes is 25% of the total time needed. %
100
___ is of __ =
Set up a proportion. The “of” part is what you have been asked to find. 25
100
___ 20 m __ =
100 • 20 = 25 • m
The cross products are equal.

11. Additional Example 2 Continued
m is multiplied by 25.
2,000 25
_____
25m 25
____
Divide both sides by 25 to undo multiplication. =
80 = m
The time needed for the exercises is 80 min. So far, the exercises have taken 20 min. Because – 20 = 60, Johan will be finished in 60 min.

12. Check It Out: Example 2
Phil is 30% of the way through his homework. If he has worked for 15 minutes so far, how much longer does he have to work?
30% of the exercises are completed, so 15 minutes is 30% of the total time needed. %
100
___ is of __ =
Set up a proportion. The “of” part is what you have been asked to find. 30
100
___ 15 m __ =
100 • 15 = 30 • m
The cross products are equal.

13. Check It Out: Example 2 Continued
m is multiplied by 30.
1,500 30
_____
30m 30
____
Divide both sides by 30 to undo multiplication. =
50 = m
The time needed for the homework is 50 min. So far, the homework has taken 15 min. Because – 15 = 35, Phil will be finished in 35 min.

14. Instead of using proportions, you can also multiply to find a percent of a number.

15. Additional Example 3: Multiplying to Find a Percent of a Number
Find 36% of 50.
36% = 0.36
Write the percent as a decimal.
0.36 • 50
Multiply using the decimal. 18
So 18 is 36% of 50.
Check
Use a model to check the answer.
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

16. Write the percent as a decimal.
Check It Out: Example 3
Find 20% of 70.
20% = 0.20
Write the percent as a decimal.
0.20 • 70
Multiply using the decimal. 14
So 14 is 20% of 70.
Check
Use a model to check the answer.
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

17. Lesson Quizzes
Standard Lesson Quiz
Lesson Quiz for Student Response Systems

18. Lesson Quiz
1. Find 28% of 310.
2. Find 70% of 542.
3. Martha is taking a 100-question test. She has completed 60% of the test in 45 minutes. How much longer will it take her to finish the test?
4. Crystal has a collection of 72 pennies. If 25% of them are Canadian, how many Canadian pennies does she have?
86.8
379.4
30 min 18

19. Lesson Quiz for Student Response Systems
1. Identify 35% of 260.
A B. 91
C D. 295

20. Lesson Quiz for Student Response Systems
2. Identify 60% of 422.
A B. 482
C D

21. Lesson Quiz for Student Response Systems
3. Ella has to draw a flowchart as a part of an assignment. She has drawn 40% of the flowchart in 10 minutes. How much longer will it take her to complete the flowchart?
A. 10 min B. 25 min
C. 15 min D. 35 min

22. Lesson Quiz for Student Response Systems
4. Of 80 sheep in a field, 65% are ewes. How many ewes are there in the field?
A. 28 ewes B. 52 ewes
C. 65 ewes D. 108 ewes