Question

A 20% antifreeze solution is to be mixed with a 90% antifreeze solution to get 7 liters of a 50% solution. How many liters of the 20% and how many liters of the 90% solutions will be used?

Answer 1

0.2x + 0.9 ( 7 - x )= 0.5 * 7

0.2x + 6.3 - 0.9x = 3.5

Combine like terms:

0.2x - 0.9x = 3.5 - 6.3

-0.7x = -2.8

x = -2.8/-0.7

x = 4

x = 4 liters of 20% solution needed

7-x = 7-4 = 3 liters of 90% solution needed