Question

In a box of pens there are 3 green pens for every 4 blue pens.

There are 15 green pens in the box. how many blue pens are there?

Answer 1

20 blue pens

Explanation:

Since it is a 3 to 4 ratio (Green to Blue) and you have 15 green pens you need to multiply 5 to the 3(green pens). Since you multiplied 5 it needs to stay equal you need to multiply 5 to the blue pens which would give you 20 blue pens

Answer 2

Let's use x to represent the number of blue pens in the box.

We know that there are 3 green pens for every 4 blue pens.

So, we can set up the following proportion:

3/4 = 15/x

To solve for x, we can cross-multiply:

3x = 60

Then, we can divide both sides by 3:

x = 20

Therefore, there are 20 blue pens in the box.