Question

Two pumps working together drain a pool in `6` hours. If older pump itself drains out the pool in `14` hours, how much time will newer pump take to drain the pool?

Answer 1

Newer pump can drain out the pool in `10 1/2` hours.

Explanation:

As two pumps working together drain the pool in `6` hours,

in one hour, they drain `1/6` of the pool.

As older pump itself drains the pool in `14` hours

as such in one hour, older pump can drain `1/14` of the pool.

As in one hour, two pumps together drain out `1/6` of the pool and older pump drains out `1/14` of the pool

newer pump on its own must be draining

`1/6-1/14=(7-3)/42=4/42=2/21` of the pool

Hence, newer pump can drain out the pool in `21/2=10 1/2` hours.