45% of what number is 18

Step by step

The question

Question: 18 is 45% of what number?

We write it like this: 45% of the number is 18.

18 is a part.

The whole number is what we want.

Careful!

Many people work out 45% of 18.

But 18 is not the whole.

It is only 45% of it.

1 Write the percent as a fraction

Percent means out of 100.

So 45% is 45/100.

45 and 100 can both be divided by 5.

So 45% is 9/20: 9 of 20 equal parts.

2 Draw the whole

3 Find one part

9 parts make 18.

So one part is 18 divided by 9.

That is 2.

Every part is 2.

4 Find the whole

The whole is 20 parts.

20 times 2 is 40.

So 18 is 45% of 40.

5 Check

Let's check: is 45% of 40 really 18?

45% is 9/20.

Of means times.

40 divided by 20 is 2.

9 times 2 is 18.

We get 18.

So it is right!

Let's look back.

First: write the percent as a fraction.

Then: draw the whole.

Then: find one part.

Then: find the whole.

Last: check.