Filling Up on GMAT Quant

Problem Solving: GMAT Question of the Day
Nested Function Fun: GMAT Question of the Day
March 25, 2015
QOD2015_0330
The Product of GMAT Practice
March 30, 2015
Show all

Filling Up on GMAT Quant

QOD2015_0327
Explanation
If the first valve pumps x cubic feet of gas per minute, then the two valves together will pump x + x + 20 cubic feet of gas per minute. At the first rate, x , the tank reaches capacity in 120 minutes; at the second, 2x + 20, it takes only 50 minutes. So: Capacity = x * 120 = (x + x + 20) * 50 We can solve for the rate of the first valve: 120x = 50 * 2x + 1000 20x = 1000 x = 50 Since the lone valve fills in 120 minutes, the capacity is 120 * 50 = 6000. The correct answer is (B).