Question

70% of what number is 21 and how do you do it

Answer 1

The answer is 30 because you put 21/x= 70/100
you cross multiply 100 and 21 you get 2100 and you divide it by 70 you should get 30 cause you take out one 0 from both numbers and end up with 210 divided by 7 then you get 30

Answer 2

70 % of unknown number = 21
We multiply the percentage by a variable and make it = to the given value.
70% of n = 21
Change percent to decimal
70% = $\frac{70}{100}$ = 0.7
0.7n = 21
divide either sides by 0.7 to isolate n

$\frac{0.7n}{0.7}$ = $\frac{21}{0.7}$
0.7 and 0.7 cancels out
n = 30

0.7 × 30 = 21
70 % of 30 is 21
An example has been attached below

% of a number = multiply % by number
value is the % of a number = divide % by value