18 is what percent of 80?

1 Answer
Jun 5, 2017

18 is 22.5% of 80.

Explanation:

The way I am going to solve this is through fractions.

As we should all know, x% = x/100

this means that we can make this equation:

18/80 = x/100

We can solve this by finding out how 18/80 gets to x/100

(18 xx y = x)/(80 xx y = 100

In this equation, it is important to remind you that y in all parts of this equation are the same.

This means that you need to multiply 80 to get to 100 by the same number as you need to multiply 80 to get to x. Now we can solve the equation.

First, we find out what y is from simple algebra working on the denominator of the equation.

80 xx y = 100

We can move 80 to the other side by dividing each side by 80

cancel(80)/cancel(80) xx y = 100/80

y = 100 ÷ 80

color(lime)(y = 1.25

Now we can input 1.25 in for y.

(18 xx y = x)/(80 xx y = 100

(18 xx 1.25 = x)/(80 xx 1.25 = 100

18 xx 1.25 = x

Now we can use simple math to find x.

18 xx 1.25 = x

18 xx 1.25 = 22.5

color(blue)(x = 22.5

Now we can input x for 22.5 in the original equation.

18/80 = x/100

18/80 = 22.5/100

therefore 18 is 22.5% of 80.