30% of a number is 120. What is the number?

2 Answers
Jul 2, 2017

400400

Explanation:

You divide 120/0.3=4001200.3=400

You can double check by multiplying 400xx0.3=120400×0.3=120

Jul 2, 2017

n=400n=400

Explanation:

If we choose nn as the number, we can write an equation:

30% " of " n = 120" "larr30% of n=120 now solve for nn

30/100 xx n =12030100×n=120

n = 120 xx 100/30n=120×10030

n = 400n=400

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Or we can write equivalent fractions for the numbers and percentages as a direct proportion:

if 120120 is 30%30%, then what number will be 100%?100%?

120/30 = x/100" "(larr"numbers")/(larr"percents")12030=x100 numberspercents

30x = 120xx100" "larr30x=120×100 cross multiply to get this

x = (120xx100)/30x=120×10030

x =400x=400