Question

20% of what number is 30? Pick the proportion that could be used to solve.

Answer 1

30 is 20% of 150

Working out percentage problems of the form "30 is 20 percent of what number?"

We have, 20% × x = 30

or,  

20/100 × x = 30

Multiplying both sides by 100 and dividing both sides by 20,

we have x = 30 ×  100/20

x = 150

If you are using a calculator, simply enter 30×100÷20, which will give you the answer.