A swimming pool can be emptied in 4 hours using two pumps--a 10-horsepower pump along with a 6-horsepower pump. The 6-horsepower pump takes 6 more hours than the 10-horsepower pump to empty the pool alone. How long would it take the 10-horsepower pump to empty the pool alone?
A) 9 hrs
B) 7 hrs
C) 6 hrs
D) 8 hrs
E) none of these

Question

Quizplus · Accepted Answer

Let x be the time it takes for the 10-horsepower pump to empty the pool alone. Then, the 6-horsepower pump takes x + 6 hours. The combined rate of the pumps is 1/4 of the pool per hour. The equation is 1/x + 1/(x+6) = 1/4. Solving this equation gives x = 6 hours.

A Swimming Pool Can Be Emptied in 4 Hours Using