GMAT Club Official Solution:Two uniform cleaning solutions contain only cleaning concentrate and water. In solution A, the ratio of cleaning concentrate to water is 1 to 3. In solution B, the ratio of cleaning concentrate to water is 2 to 3. If 24 liters of solution A are poured into solution B, what is the ratio of cleaning concentrate to water in the resulting solution B?(1) After the 24 liters are added, solution B contains 18 liters more water than cleaning concentrate.
Since in solution A, the ratio of cleaning concentrate to water is 1 to 3, the 24 liters from solution A contain 6 liters of cleaning concentrate and 18 liters of water.
Let the amounts of cleaning concentrate and water in solution B be 2x and 3x.
After the addition:
Cleaning concentrate = 2x + 6
Water = 3x + 18
So:
(3x + 18) - (2x + 6) = 18
x + 12 = 18
x = 6
Thus, after the addition, solution B contains 18 liters of cleaning concentrate and 36 liters of water. Therefore, the ratio of cleaning concentrate to water is:
18 : 36 = 1 : 2
Sufficient.
(2) Before the 24 liters are added, solution B contains 6 liters more water than cleaning concentrate.
Since solution B has cleaning concentrate and water in the ratio 2 to 3, solution B contains 12 liters of cleaning concentrate and 18 liters of water.
The 24 liters from solution A contain 6 liters of cleaning concentrate and 18 liters of water. So after the addition, solution B contains:
12 + 6 = 18 liters of cleaning concentrate
and
18 + 18 = 36 liters of water.
Therefore, the ratio of cleaning concentrate to water is:
18 : 36 = 1 : 2
Sufficient.
Answer: D.