FRAME 3-33.
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.
____________________________________________________________________________________
FRAME 3-34.
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?"
____________________________________________________________________________________
MD0900
3-19