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

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

by BTGmoderatorDC » Tue Feb 26, 2019 9:53 pm

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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

OA A

Source: Magoosh
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by Jay@ManhattanReview » Tue Feb 26, 2019 10:11 pm
BTGmoderatorDC wrote: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

OA A

Source: Magoosh
Work done by pump A and B together in 1 hour = 1/3 + 1/2 = 5/6 part of the pool

Thus, it takes 1 / (5/6) = 6/5 hours or (6/5)*60 = 72 minutes to empty the pool

The correct answer: A

Hope this helps!

-Jay
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Let the total work be 1

by swerve » Wed Feb 27, 2019 7:06 am
Let the total work be 1
Rate of work A = Total work done/ Total time taken \(= 1/3\)
Rate of work B = Total work done/ Total time taken \(= 1/2\)

Total Rate \(= 1/2 + 1/3 = 5/6\)
In 1 hour work done is \(= 5/6\)
Time taken to complete the entire work (1) \(= 6/5\) hours

\((6/5)*60=72\) minutes.
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