Question

The ratio of the number of math books to the number of comic books on a shelf is 7:3. There are 21 comic books on the shelf. Find the number of math books on the shelf.

Answer 1

`49`

Explanation:

Let the number of math books on the shelf be
`x`.

`7:3\\x:21`

Cross multiply the ratio and solve for
`x`.

`3x=7 * 21\\3x=147\\x=49`

There are 49 math books on the shelf.

Answer 2

There are 49 math books on the shelf.

Explanation:

math books : comic books

`7` :
`3`

`x` :
`21`

`21`÷
`3=7`

`7*7=49`

`x=49`