Posted by marissa on .
how many quarts of pineapple juice should Theo add to a 20% pineapple drink to create 5 quarts of a 50% pineapple juice mixture?

algebra 
MathMate,
In 5 quarts of 50% mixture, there are 2.5 quarts of water.
The amount of 20% drink that contains 2.5 quart of water is 2.5/(10.20) = 3.125 quarts.
So Theo will need 1.875 quarts of pure pineapple juice, and 3.125 quarts of 20% drink to make 5 quarts of 50% mixture.