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Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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23 Mar 2015, 06:34
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93% (00:49) correct 7% (00:56) wrong based on 153 sessions
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Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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23 Mar 2015, 08:02
Pump A can empty the pool in 3 hours therefore the rate at which it empties is 1/3 pool/hour Pump b can empty the pool in 2 hours therefore the rate at which it empties is 1/2 pool/hour.
If they work together, the resulting rate is the addition of both rates (1/3 +1/2)pool/hour = 5/6 pool/hour
Now we have the following:
(5/6pool)/60min = 1pool/x
x = 72minutes
Answer is A



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Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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23 Mar 2015, 08:16
Bunuel 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
Kudos for a correct solution. Speed of B is 1.5 times of A . combined speed B+A = 1.5A + A = \(\frac{5}{2}\) A . so if ideally A takes 3 hrs , with \(\frac{5}{2}\) *A speed it will take > \(\frac{3*2}{5}* 60\) = 72 minutes. Answer A.
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Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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23 Mar 2015, 08:58
Rate of A: \(\frac{1}{3h}\) Rate of B: \(\frac{1}{2h}\) Combined rate: \(\frac{1}{3h}+\frac{1}{2h}=\frac{5}{6h}=\frac{5}{360 minutes}=\frac{1}{72 minutes}\)
Answer A is correct



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Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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24 Mar 2015, 02:50
Answer = A = 72 Rate of pump A \(= \frac{1}{180}\) Rate of pump B = \(\frac{1}{120}\) Combined rate \(= \frac{5}{360}\) Time required for combined work \(= \frac{360}{5} = 72\)
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Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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24 Mar 2015, 10:55
Bunuel 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
Kudos for a correct solution. 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. Answer A



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Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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25 Mar 2015, 21:21
Hi All, In this prompt, we have two 'entities' sharing a task (with no *twists*), so the Work Formula will be perfect for this question. Work = (A)(B)/(A+B) where A and B are the rates of the two entities. We're given the respective rates for two pumps to empty a pool: Pump A can empty the pool in 3 hours. Pump B can empty the pool in 2 hours. We're asked how long it takes the two pumps, working together, to empty the pool. Plugging in the respective numbers (the 3 and the 2), we have... (3)(2)/(3+2) = 6/5 = 1.2 hours = 1 hour 12 minutes The question asks for an answer in MINUTES. 1 hour 12 minutes = 72 minutes. Final Answer: GMAT assassins aren't born, they're made, Rich
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Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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25 Mar 2015, 21:36
Combined rate is 1/3+1/2 is 5/6.
time taken to empty pool is 6/5*60 = 72 Mins Answer is A



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Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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25 Mar 2015, 23:46
Total Work Done in 1 hr = (1/2) +(1/3) Total time in minutes = 6/5 *60 = 72 minutes Ans : A
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Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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25 Mar 2015, 23:59
Bunuel 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
Kudos for a correct solution. +1 for A IN 1 hour, Pump A can empty=1/3 of the pool In 1 hour, Pump B can empty=1/2 of the pool Working together, in 1 hour, they can empty=1/3+1/2=5/6 of the pool Therefore, to empty the pool. both will take=6/5 Hours=6/5*60 minutes=72



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Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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30 Mar 2015, 03:31



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Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump [#permalink]
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