How many liters of each should be mixed together in order to get 15L that is 13% orange juice?

Question

One canned juice drink is 20% orange juice; and another is 5% orange juice. How many liters of each should be mixed together in order to get 15L that is 13% orange juice?

Answer 1

You need to make a system of equations.  One equation for the total volumes, and another for the amount of juice in the solutions.

 

X + Y = 15

.20X + .05Y = .13*15

 

When you solve this system you find that X=8 and Y=7