Question

How many quarts of pure antifreeze must be added to 6 quarts of a 20% antifreeze solution to obtain a 60%

antifreeze solution? (Hint: pure antifreeze is 100% antifreeze.)
...

Answer 1

6 quarts

Explanation:

You want to know the number of quarts of 100% antifreeze to add to 6 quarts of 20% antifreeze to make a 60% solution.

Setup

Let x represent the number of quarts of 100% antifreeze added to the solution. Then the total amount of antifreeze in the mixture is ...

20%(6) +100%(x) = 60%(6 +x)

Solution

Simplifying the equation, we have ...

1.2 +x = 3.6 +0.6x

0.4x = 2.4 . . . . . . . . . subtract 0.6x+1.2 from both sides

x = 6 . . . . . . . . . . divide by 0.4

6 quarts of pure antifreeze must be added.