Question

two water pumps are used to drain a swimming pool pump a can drain the pool in 45 minutes in pump be Can Dream the same pool in 35 minutes how many minutes will it take to drain the pool using both pumps at the same time

Answer 1

Pump A = 45 mins

Pump B = 35 mins

Pump A and B = (45 x 35) / ( 45 + 35) = 19.69 mins (nearest hundredth)

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Answer: 19.69 mins

Answer 2

We're looking for the amount of time involved. We know the pumping rates.

First, a look at the units of measurement:

1 job

-----------------------

rate#1 + rate#2 (both in job / time)

When this is simplified, "job" disappears (is cancelled) and time appears in the numerator of the result.

Now, using the actual numbers given:

1 job

-----------------------

1 job 1 job

----------- + ---------------- = 0.0508 job/min

45 min 35 min

Finally, divide "1 job) in the first numerator by this 0.0508 job/min. The result, 19.69, indicates the number of minutes required for both pumps to drain the pool.