Step by step
The question
Question: 12 is 30% of what number?
30% of ? = 12
We write it like this: 30% of the number is 12.
12 is a part.
The whole number is what we want.
? = the whole number
Careful!
Many people work out 30% of 12.
But 12 is not the whole.
It is only 30% of it.
Careful: not 30% of 12 ✗
1 Write the percent as a fraction
Percent means out of 100.
So 30% is 30/100.
30% = 30100
30 and 100 can both be divided by 10.
So 30% is 3/10: 3 of 10 equal parts.
= 30 ÷ 10100 ÷ 10 = 310
2 Draw the whole
3 Find one part
3 parts make 12.
So one part is 12 divided by 3.
That is 4.
1 part = 12 ÷ 3 = 4
Every part is 4.
4 Find the whole
The whole is 10 parts.
10 times 4 is 40.
10 parts = 10 × 4 = 40
So 12 is 30% of 40.
5 Check
Let's check: is 30% of 40 really 12?
30% is 3/10.
Of means times.
40 divided by 10 is 4.
3 times 4 is 12.
30% of 40 = 310 × 40 = 3 × 4 = 12 (40 ÷ 10 = 4)
We get 12.
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.
Answer
10 parts = 10 × 4 = 40