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Working alone at its constant rate, pump x pumped out 1/3 of the water [#permalink]
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22 Jan 2017, 14:57
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Difficulty:
15% (low)
Question Stats:
82% (01:26) correct 18% (01:45) wrong based on 199 sessions
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Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?
I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water [#permalink]
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22 Jan 2017, 16:13
3
3
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?
I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.
A: 18 B: 24 C: 36 D: 48 E: 52
Hi
Three steps that will get you to answer.. 1) time of pump x.. 1/3 in 4 hrs, so complete in 4*3=12 hrs
2) combined time of x and y.. (1-1/3) or 2/3 in 6 hrs, so complete in 6*3/2=9 hrs..
3) finally our answer or pump y.. 1/(combined time) - 1/(time of pump x)= 1/9-1/12=1/36.. So 36hrs
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water [#permalink]
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22 Jan 2017, 16:43
chetan2u wrote:
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?
I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.
A: 18 B: 24 C: 36 D: 48 E: 52
Hi
Three steps that will get you to answer.. 1) time of pump x.. 1/3 in 4 hrs, so complete in 4*3=12 hrs
2) combined time of x and y.. (1-1/3) or 2/3 in 6 hrs, so complete in 6*3/2=9 hrs..
3) finally our answer or pump y.. 1/(combined time) - 1/(time of pump x)= 1/9-1/12=1/36.. So 36hrs
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water [#permalink]
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23 Jan 2017, 01:16
2
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?
I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water [#permalink]
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23 Jan 2017, 12:12
Bunuel wrote:
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?
I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water [#permalink]
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23 Jan 2017, 12:40
1
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?
A: 18 B: 24 C: 36 D: 48 E: 52
rate of x=1/12 rate of x and y=1/9 rate of y=1/9-1/12=1/36 36 hours C
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water [#permalink]
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25 Jan 2017, 10:16
1
3
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?
A: 18 B: 24 C: 36 D: 48 E: 52
We are given that pump X pumped out 1/3 of the water in a pool in 4 hours. Since rate = work/time, the rate of pump X is (1/3)/4 = 1/12. Also, since 1/3 of the water was pumped out of the pool, 2/3 was left to be removed.
Since pump X and Y pumped out 2/3 of the water in 6 hours, the combined rate of pumps X and Y is (2/3)/6 = 2/18 = 1/9.
Finally, since rate of pump X + rate of pump Y = the combined rate of pumps X and Y, the rate of pump Y is:
1/9 - 1/12 = 4/36 - 3/36 = 1/36
Thus, pump Y can pump all the water out of the pool in 36 hours.
Answer: C
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Re: Working alone at its constant rate, pump x pumped out 1/3 of the water [#permalink]
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14 Apr 2017, 14:03
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?
I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.
A: 18 B: 24 C: 36 D: 48 E: 52
1/X (amount of work done by X in 1h)= (1/3)/4=1/12 Now, there are 2/3 of work left to be done. (1/X)+(1/Y)=(2/3)/6 (1/12)+(1/Y)=1/9 (1/Y)=(12/108)-(9/108)=3/108=1/36 Time = reciprocal of rate (work done in one hour) = 36h. C
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water [#permalink]
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30 May 2018, 18:32
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