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Lesson 30  Section 2

WHAT PERCENT?

Back to Section 1

We have seen:

To change a number to a percent, multiply it by 100, and add the % sign.

.125 = 12.5%

(Lesson 4.)

A fraction is a number, obviously.  And to change a fraction to a percent, do the same.  Lesson 27.

Example 1.   What percent of $24 is $2?

Solution.  In standard form:  $2 is what percent of $24?  That is:

2 out of 24 is what percent?

Now, 2 out of 24 is the fraction    2 
24
 , which reduces to    1 
12
.

$2, then, is one twelfth of the whole $24 -- which is 100%.  We must therefore calculate one twelfth of 100%.

 1 
12
 × 100% =  100% ÷ 12.

(Lesson 11.)

"12 goes into 100 eight (8) times (96), with 4 left over."

100%
  12 
 = 8  4 
12
 = 8 1
3
%.
$2 is 8 1
3
% of $24.

 3.   What is a general method for finding the Percent?
 
  Write the fraction that has the Base as the denominator and the Amount as the numerator, and express that fraction as a percent: Lesson 27.
 
A out of B =  A
B
 × 100%

Certain fractions come up frequently, and the student should not have to multiply by 100%, but should know their percent equivalents.
See Problem 18.

Example 2.   21 is what percent of 15?

Solution.   Note first that 21 is more than 15. Therefore it will be more than 100% of 15. (Lesson 17.)  On reducing and expressing the improper fraction as a mixed number:

21
15
  =   7
5
  =  1 2
5
.
The percent will be 1 2
5
 × 100%. .

1 × 100% = 100%.

2
5
 × 100% ("Two fifths of 100%") = 40%.    Lesson 24.

21 is 140% of 15.


Please "turn" the page and do some Problems.

or

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1st Lesson on Percent

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