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

Answer:

There are 49 math books on the shelf.

Step-by-step explanation:

math books : comic books

       $7$           :         $3$

       $x$           :        $21$

$21$÷$3=7$

$7*7=49$

$x=49$

Answer 2

Answer:

$49$

Step-by-step explanation:

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

$7:3\\x:21$

Cross multiply the ratio and solve for $x$.

$3x=7 \times 21\\3x=147\\x=49$

There are 49 math books on the shelf.