Question

Pump A fills a pool in 6 hours. Pump B fills the same pool in 3 hours. How long would it take to fill the pool if both pumps were filling?

Answer 1

2 hours

Explanation:

Rate and TIme are inverse of each other.

First, lets find rates of each.

Pump A:

takes 6 hours to fill up so rate is 1/6

Pump B:

takes 3 hours to fill up so rate is 1/3

Combined rates of Pump A and Pump B:

1/6 + 1/3

The time it takes to fill up if BOTH turned on together would be the COMBINED RATE's INVERSE. Shown below the calculation:

`((1)/(6)+(1)/(3))^(-1)\\=((1)/(6)+(2)/(6))^(-1)\\=((1)/(2))^(-1)\\=2`

So, it takes 2 hours