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# HELP ME!

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12 is 15% of what number?

mathkiller  May 22, 2017
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#1
+1

12 is 15% of what number?

Let the number =N, then:

15%N = 12

0.15N = 12    divide both sides by 0.15

N =12 / 0.15

N = 80

Guest May 22, 2017
#2
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12 is 15% of 80.

Setup a proportion. Setting up a proportion allows the calculation to be simpler arithmetically:

$$\frac{12}{x}=\frac{15}{100}$$Simplify the 15/100 by dividing the numerator and denominator by the GCF, 5.

$$\frac{12}{x}=\frac{3}{20}$$Cross multiply and solve for x

$$12*20=3x$$Simplify the left hand side of the equation

$$240=3x$$ Divide by 3 on bioth sides to isolate x

$$80=x$$

TheXSquaredFactor  May 22, 2017
#3
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Both of these solutions are essentially doing the same thing

15% is .15 and as a fraction that 15/100 or 3/20 so by dividing by .15 you are basically multiplying by 20 and dividing by 3.

JonathanB  May 22, 2017

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