A 9-quart cooling system is checked and found to be filled with a solution that is 10% antifreeze. The desired strength of the solution is 70% antifreeze. How many quarts of solution need to be drained and replaced with pure antifreeze to reach the desires strength?
A) 8 qt
B) 7 qt
C) 10 qt
D) 6 qt
E) 13 qt

Question

Quizplus · Accepted Answer

To achieve a 70% antifreeze solution in a 9-quart system, the system needs to contain 6.3 quarts of antifreeze (70% of 9 quarts). Initially, it contains 0.9 quarts of antifreeze (10% of 9 quarts). By draining and replacing quarts of the initial solution with pure antifreeze, the amount of antifreeze is directly increased while keeping the total volume constant at 9 quarts. To reach 6.3 quarts of antifreeze from 0.9 quarts, one needs to replace 6 quarts of the initial solution with pure antifreeze, thus achieving the desired 70% concentration without changing the total volume of the solution.

A 9-Quart Cooling System Is Checked and Found to Be