Question

One fifth of a number is subtracted from four fifth of the same number. If the result is 9, what is the number. ​

Answer 1

Let x be the unknown number. One fifth of this number is x/5, one fourth of this number is x/4. So, we have

`(x)/(4)-(x)/(5) = (5x-4x)/(20) = (x)/(20)`

We know that this difference equals 9, so we have

`(x)/(20)=9`

Multiply both sides by 20 to get

`x=180`