Solution to

A variation of the above problems is to tell you that a number is a certain

Frame 3-32.

percent of the original number, then ask you to find the original number.

a. 3% (3/100)

For example, 25% of what number is 5? (or 5 is 25% of what number?)

Let "N" stand for the original number. The question can then be restated

b. 200% (120/60)

as 25% of N is 5. The mathematical form of this statement is 25% x N

= 5. You can either state the problem in decimal form or as a fraction:

c. 33.33% (1/3)

0.25N = 5

or

1/4 x N = 5

NOTE: 0.25N is another way of writing (0.25)(N). 1/4 is the reduced

form of 25/100.

State "Twenty percent of what number is 30?" as a decimal or fractional

equation.

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Solution to

After you have stated the problem as an equation (that is, the

Frame 3-33.

mathematical statements on both sides of the "=" symbol are equal),

solve for N. Multiply or divide both sides of the equation by the same

0.20N = 30

number or fraction in order to change one side of the equation to N (or

1N). The example can be worked as shown.

or

0.25N = 5

or

1/4 x N = 5

1/5 x N = 30

0.25N

5

N

4

5

4

=

X

=

X

0.25

0.25

4

1

1

1

1N = 20

4N

5x4

=

4

1

N = 20

Solve the problem: "Twenty percent of what number is 30?"

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MD0900

3-19

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