There are some pencils and erasers in a box. If there are 12 pencils and the ratio of pencils to erasers is 3:2, how many erasers are in the box

Question

There are some pencils and erasers on a box. If there are 12 pencils and the ratio of pencils to erasers is 3:2, how many erasers are in the box? 

Answer 1

You can set up a proportion:

 

First write down what you know: for every 3 pencils there are 2 erasers and there are 12 pencils in a box

What you want to know: How many erasers in the box

 

pencil/erasers = pencil/erasers

 

3/2 = 12/x (substitute what you know

3x = 2(12)  (cross multiply)

3x = 24 (simplify)

x = 24/3 (divide both sides by 3)

x = 8 (simplify)

 

there are 8 erasers in the box

 

check  12/8 = 3/2 (if you divide numerator and denominator by gcf  4)

 

 

 

 

Answer 2

Mariah, a proprtion is two equal ratios. Ratios are always reduced to their lowest terms. If there are 14 red chairs and 7 green, the ratio of red:green is 2:1.

 

If the ratio is 3:2, what goes with 12? 

 

12÷3 = 4

2 x 4 = 8, so there are 8 erasers.

 

12:8 = 3:2

 

Hope this helps!