Question

One pump can drain a pool in 8 minutes. when a second pump is also used, the pool only takes 4 minutes to drain. how long would it take the second pump to drain the pool if it were the only pump in use

Answer 1

Answer:

8 minutes

Step-by-step explanation:

The first pump can drain in 8 minutes, therefore:

Rate of the first pump = 1/8

Working together, they can drain the pool in 4 minutes, therefore:

Rate of both pumps = 1/4

Let the time taken by the second pump =t

Rate of the second pump = 1/t.

We then have:

$\dfrac{1}{8}+ \dfrac{1}{t}=\dfrac{1}{4}\\ Collect like terms \\\dfrac{1}{t}=\dfrac{1}{4}-\dfrac{1}{8}\\\dfrac{1}{t}=\dfrac{2-1}{8}\\\dfrac{1}{t}=\dfrac{1}{8}\\ Therefore:\\t = 8 minutes$

It would take the second pump 8 minutes to drain the pool alone.