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?

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Answer 1 · 2017-02-22T05:59:02

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

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.

Two pumps working together drain a pool in 66 hours. If older pump itself drains out the pool in 1414 hours, how much time will newer pump take to drain the pool?