Download 7th Grade Honors Percent-Proportion (by Denise

The Percent Proportion
Let’s start with what you
know:
What is the definition of a ratio?
A ratio is a comparison of 2 or
more numbers.
What is a proportion?
A proportion is an equation
containing 2 equivalent ratios.
Percent
What is the definition of percent?
Percent is a ratio where the 2nd
number is 100. So, a number out of
100 is another way of defining
percent.
The Percent Proportion
%
100
=
IS (Part)
OF Whole
Many percent problems can be
solved using this proportion.
Let’s look at some examples.
Take a look at the 3 different types
of percent proportion problems
below:
%/100 = is/of
1.What is 60% of 80?
2.What percent of 75 is 15?
3.12 is 55% of what number?
1. What is 60% of 80?
Using the percent proportion, we see in this
problem that we know a) the percent and
b) the “of”. We always know that we have
the number 100. So, the part we are missing
is the “is”.
So:
60 = x Cross multiply to solve.
100 80 100x = 60 • 80 or 4800
Solve for x and you get x = 48.
2. What percent of 75 is
15?
Set up your proportion for this
problem.
What are the 3 parts you know?
So x = 15
100 75
Solve this by cross multiplying.
3. 12 is 55% of what
number?
What 3 parts do we know?
Set up your proportion and solve
by cross-multiplying.
(Round to the nearest 100ths place)
Let’s try some applications
Example 1.
Mark sells appliances. He earns
8% commission on sales. If he
sells $4000 worth of appliances,
how much commission does he
make?
Example 2
Ryan was practicing his
free throws. He made 27
out of 40 shots. What was
his free throw percentage?
Example 3:
The value of gold today is 180%
of its value three years ago. If a
gold chain was worth $90 three
years ago, what is it worth today?
Let’s Review
*A percent is a number out of 100.
*The percent proportion is the %
over 100 set equal to “is” over
“of”. (or the part over the whole)
*We will be given 3 of the 4 parts of the
proportion to set it up.
*Cross multiply and divide to solve.