Question

At a constant rate of flow, it takes 20 minutes to fill a swimming pool if a large hose is used and 30 minutes if a small hose is used.

At these constant rates, how many minutes will it take to fill the pool when both hoses are used simultaneously?

A) 10 B) 12 C) 15 D) 25 E) 50

Answer 1

B

Explanation:

Firstly, let’s say they are to fill a total of x liters, rate for big hose would be x/20 while for small hose it would be x/30.

Now if they are to work combined, total time would be

x/20 + x/30 = 5x/60 = x/12

Hence, it will take them 12 minutes