One pipe can fill a pool four times faster than a second pipe.

One pipe can fill a pool four times faster than a second pipe. When both pipes are opened, they fill the pool in eight hours. How long would it take to fill the pool if only the faster pipe is used?

Quiz

Answer/Solution

10 hr

Steps/Work

fast pipe + slow pipe = together
One pipe fills the pool four times faster than the other pipe so,
hourly fill rates:
1/x + 1/4x = 1/8
Let x = number of hours it would take the fast pipe to fill the pool thus,
x=10 hours
Answer: C