Question

A teacher had 12 purple pens if the ratio of purple pens to blue pens she owned was 4:1 how many pens did she have total?

Answer 1

15

Explanation:

Using cross multiplication, this is what I came up with:

`(4)/(1)` x
`(12)/(x)`

Or, 4x=12.

To make x be on it's own, we will divide 12 by 4, therefore removing the 4 from the right side of the equation. Since x = 3, we add that number to the total of purple pens, giving us a total of 15.

Answer 2

12 purple pens = 4 parts
1 part = 12/4 = 3
4 parts purple + 1 part blue = 5 parts
3 x 5 = 15