Author 
Message 
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 49493

Working alone, pump A can empty a pool in 3 hours. Working alone, pump
[#permalink]
Show Tags
23 Mar 2015, 06:34
Question Stats:
95% (01:12) correct 5% (01:52) wrong based on 155 sessions
HideShow timer Statistics



Current Student
Joined: 21 Aug 2014
Posts: 155
Location: United States
Concentration: Other, Operations
GMAT 1: 700 Q47 V40 GMAT 2: 690 Q44 V40
WE: Science (Pharmaceuticals and Biotech)

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



Director
Joined: 07 Aug 2011
Posts: 552
Concentration: International Business, Technology

Working alone, pump A can empty a pool in 3 hours. Working alone, pump
[#permalink]
Show Tags
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.
_________________
Thanks, Lucky
_______________________________________________________ Kindly press the to appreciate my post !!



Intern
Joined: 20 Mar 2015
Posts: 18
Location: Italy
GPA: 3.7

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



SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1834
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)

Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump
[#permalink]
Show Tags
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 \(= \frac{360}{5} = 72\)
_________________
Kindly press "+1 Kudos" to appreciate



Current Student
Joined: 06 Mar 2014
Posts: 252
Location: India
GMAT Date: 04302015

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



EMPOWERgmat Instructor
Status: GMAT Assassin/CoFounder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 12459
Location: United States (CA)

Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump
[#permalink]
Show Tags
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
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com
Rich Cohen
CoFounder & GMAT Assassin
Special Offer: Save $75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/
***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************



Intern
Joined: 02 Jan 2014
Posts: 39

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



Manager
Joined: 06 Jan 2014
Posts: 62

Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump
[#permalink]
Show Tags
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
_________________
______________________________ Liked the Post !!!! KUDOs Plzzzzz



Director
Joined: 21 May 2013
Posts: 647

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



Math Expert
Joined: 02 Sep 2009
Posts: 49493

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



NonHuman User
Joined: 09 Sep 2013
Posts: 8194

Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump
[#permalink]
Show Tags
21 Jan 2018, 15:26
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Books  GMAT Club Tests  Best Prices on GMAT Courses  GMAT Mobile App  Math Resources  Verbal Resources




Re: Working alone, pump A can empty a pool in 3 hours. Working alone, pump &nbs
[#permalink]
21 Jan 2018, 15:26






