1. Solving Percent Problems Using Proportions
Chapter 6
Section 6.5

3. Objective
The students will use proportions to solve problems involving percents.

4. Concept If we want to know what percent of 10 is 4.
We set it up into ratios
4 of 10 or 4 10
To calculate the percent we find a proportional ratio
So what % or 𝑛 100
So we have = 𝑛 100
Cross multiply to get 10(n)=4(100) then divide by 10 to get n= 40
Thus 4 out 10 is 40%

5. Find a percent. What percent of 2000 is 204.
Setup ratios  of 2000 
n of  𝑛 100
Write a proportion  = 𝑛 100
Cross multiply  2000(n) = 204(100)
Divide by 2000 𝑛 =
Simplify  n = so 204 of 2000 is 10.2%

6. Example
What percent of 92 is 23?
What percent of 15 is 6?

7. Concept- Finding a part of the whole
If we want to know what 20% of 50 is.
We set it up into ratios
n of 50 or 𝑛 50
To calculate a part of the whole we find a proportional ratio
Use 20% or
So we have 𝑛 50 =
Cross multiply to get 100(n)=50(20) then divide by 100 to get n= 10
Thus 20% of 50 is 10.

8. Example
What is 20% of 55?
What 85% of 20?

9. Concept- Finding the whole
If we want 25% of what is 5.
We set it up into ratios
5 of n or 5 𝑛
To calculate the whole
Use 25% or
So we have 5 𝑛 =
Cross multiply to get 25(n)=5(100) then divide by 25 to get n= 20
Thus 25% of 20 is 5.

10. Example
18% of what is 9?
36% of what is 54?

11. Questions?

12. Exit Ticket What percent of 25 is 5? What is 30% of 60?
7 is 25% of what?

13. Worksheet