Question

`"25%"` of a number is `21`. What is the number?

Answer 1

`x=84`

Explanation:

First convert `25%` to its decimal number.

`25%=25/100=1/4=0.25`

`25%` "of" a number means to multiply `25%` by that number. Let `x` be the number.

`0.25x=21`

Divide both sides by `0.25`.

`color(red)cancel(color(black)(0.25))^1/color(red)cancel(color(black)(0.25))^1x=21/0.25`

Simplify.

`x=84`

Answer 2

See a solution process below:

Explanation:

"Percent" or "%" means "out of 100" or "per 100", Therefore 25% can be written as `25/100`.

When dealing with percents the word "of" means "times" or "to multiply".

Finally, lets call the number we are looking for "n".

Putting this altogether we can write this equation and solve for `n` while keeping the equation balanced:

`25/100 xx n = 21`

`color(red)(100)/color(blue)(25) xx 25/100 xx n = color(red)(100)/color(blue)(25) xx 21`

`cancel(color(red)(100))/cancel(color(blue)(25)) xx color(blue)(cancel(color(black)(25)))/color(red)(cancel(color(black)(100))) xx n = 2100/color(blue)(25)`

`n = 84`

25% of `color(red)(84)` is 21