Download PROP Lesson 16 Luke

Solve % with Proportions
Solve each proportion.
x 8
1.

3 12
2.
3.
Convert 24% to a decimal
Number of Students
9
7
5
3
1
5
10
miles
15
20
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.
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?


57
57% 
100
39
Make a Ratio out of your score…
Whole
55
What % did you get?
39 55  0.70909090  71%
Part

Solve this proportion…

Write this down !!!
?
39

100 55
%
part

100 whole
OR
%
is

100 of
Example 1
What is 24 %
of 75 ?
24

=
Write the proportion.
100

Solve
x  24  75 100
x = 18

Check:
?
18  0.24  75
75
Example 2
31 is 62 % of what number?

Write the proportion.

Solve.
62 31

100 x
x  100  31 62
x = 50

Check:
31  0.62  50
Example 3
45% = 0.45
What percent of 40 is 18?

Write the proportion.

Solve.
x  100 18  40
◦ x = 45

Check:
0.45  40  18
x
18

100 40
Example 4
In 2006, people over the age of 65 made up
13% of the population in Oregon.
Total
always
goes on the
bottom !!!
The total population in Oregon in 2006
13
was approximately 3,700,000.
13% 
100
Find the number of people over 65.
13
x

100 3,700,000
 Write the percent as a fraction.

Write a proportion.

Use cross products to solve.
100x = 48,100,000
x = 481,000
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.
ALL % problems can be solved with proportions
To find the percent, part or whole value for 58
numbers in a
58% 
percent problem:
100
1.
Write the percent as a ratio.
2.
Write the ratio for the part of a number to its whole value.
3.
% frompart
Write a proportion using the ratios
Steps 1 and 2.
4.
Solve the proportion.
100

whole