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# Working alone, pump A can empty a pool in 3 hours. Working a

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Senior Manager
Joined: 20 May 2014
Posts: 282
Followers: 15

Kudos [?]: 49 [0], given: 220

Working alone, pump A can empty a pool in 3 hours. Working a [#permalink]  26 Oct 2017, 02:32
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Question Stats:

100% (01:07) correct 0% (00:00) wrong based on 2 sessions
Working alone, pump A can empty a pool in 3 hours. Working alone, pump B can empty the same pool in 2 hours. Working together, how many minutes will it take pump A and pump B to empty the pool?

A. 72
B. 75
C. 84
D. 96
E. 108

Kudos for correct solution.
[Reveal] Spoiler: OA
Director
Joined: 03 Sep 2017
Posts: 521
Followers: 1

Kudos [?]: 330 [0], given: 66

Re: Working alone, pump A can empty a pool in 3 hours. Working a [#permalink]  26 Oct 2017, 04:39
The combined rate of the two pumps is the sum of their rates, i.e. $$\frac{1}{3}+\frac{1}{2}=\frac{5}{6}$$. Then, the minutes needed to empty the pool are $$\frac{6}{5}*60 = 72$$ (we multiply by 60 since the rates are in hours).

Re: Working alone, pump A can empty a pool in 3 hours. Working a   [#permalink] 26 Oct 2017, 04:39
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