Solve % with Proportions

Solve each proportion.1.

2. Convert 24% to a decimal

3. Morgan organized a fundraiser that required students to earn money for running miles around the track on a Saturday. The histogram above shows the number of students who ran various intervals of miles.

a) How many students ran in the fundraiser?b) Which mile range represents the largest group?c) Find the probability that a randomly chosen student from the

fundraiser ran at least 5 miles but less than 10 miles.

12

8

3x

1

3

5

7

9

5 10 15 20miles

ALL % problems can be solved with proportions

a Ratio is …◦ a Fraction

a Proportion is …◦ 2 = fractions

% means …◦ Out of 100, per 100, over 100

Write 57% as a Ratio … If you got 39 out of 55 on a test,◦ What part did you get right?◦ What was the whole test worth?

Make a Ratio out of your score… What % did you get?

100

57%57

55

39

5539 70909090.0 %71

Part

Whole

=

Solve this proportion…

Write this down !!!

55

39

100

?

whole

part

100

%

of

is

100

%

OR

What is 24 % of 75 ?

Write the proportion.

Solve

x = 18

Check:

Example 1

100=

?24

75

7524.018

1007524 x

31 is 62 % of what number?

Write the proportion.

Solve.

x = 50

Check:

x

31

100

62

Example 2

6231100 x

5062.031

What percent of 40 is 18?

Write the proportion.

Solve.

◦x = 45

Check:

40

18

100

x

Example 3

4018100 x

184045.0

45% = 0.45

In 2006, people over the age of 65 made up 13% of the population in Oregon.

The total population in Oregon in 2006 was approximately 3,700,000.

Find the number of people over 65.

Write the percent as a fraction.

Write a proportion.

Use cross products to solve. 100x = 48,100,000 x = 481,000

There were approximately 481,000 people over 65.

000,700,3100

13 x

100

13%13

Example 4

Total always

goes on the bottom !!!

1. What is 20% of 60?

2. What percent of 84 is 42?

3. Sixteen is 25% of what number?

When have you or someone you know used a percent to calculate a discount? How did you do it?

Targets: Find the percent of a number using proportions.

Find a missing number using proportions with percents.

To find the percent, part or whole value for numbers in a percent problem:

1. Write the percent as a ratio.

2. Write the ratio for the part of a number to its whole value.

3. Write a proportion using the ratios from Steps 1 and 2.

4. Solve the proportion.

whole

part

100

%

ALL % problems can be solved with proportions

100

58%58