Question

A new type of pump ca drain a certain pool in 6 hours. An older pump can drain the pool in 9 hours. How long will it take both pumps working together to drain the pool. Do not do any rounding off.
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Answer 1

Answer:

Let a be the number of hours it takes for both pumps to drain a certain pool.

The new type pump has a rate of

1

6

of a certain pool per hour.

The older pump has a rate of

1

9

of a certain pool per hour.

Together, the rate of the two pumps is

1

a

of a certain pool per hour.

The amount of work done by the two pumps in one hour is equal to the work done by the two pumps in one hour combined.

• 1

The two pumps can drain a certain pool in

18

5

hours.