Question

Shirley wants to make doughnuts. She needs 2 ounces of jelly to make a doughnut.

Jelly comes in 8-ounce jars. If she wants to make 20 doughnuts, how many jars does she need to buy?

Answer 1

5 jars

Explanation:

If 2 ounces of jelly make a doughnut, then 8 ounces of jelly make 4 doughnuts, because 8/4 = 2. However, she wants to make 20 doughnuts. So, if 1 jar makes 4 doughnuts, then 5 jars make 20 doughnuts.

You could also do it by ounces. If a doughnut requires 2 ounces of jelly, 20 doughnuts require 40 ounces of jelly (20*2=4). Then, if there are 8 ounces of jelly in a jar, then 40/8 = 5 jars cover 40 ounces.