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At their respective rates, pump A, B, and C can fulfill an [#permalink]
02 Apr 2009, 19:12

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At their respective rates, pump A, B, and C can fulfill an empty tank, or pump-out the full tank in 2, 3, and 6 hours. If A and B are used to pump-out water from the half-full tank, while C is used to fill water into the tank, in how many hours, the tank will be empty?

Re: PS: Pool fills [#permalink]
03 Apr 2009, 06:51

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Economist wrote:

At their respective rates, pump A, B, and C can fulfill an empty tank, or pump-out the full tank in 2, 3, and 6 hours. If A and B are used to pump-out water from the half-full tank, while C is used to fill water into the tank, in how many hours, the tank will be empty? A. 2/3 B. 1 C. 3/4 D. 3/2 E. 2

You can use a rates formula here, or convert each worker to the same amount of time (6 hours) :

A empties 3 tanks every 6 hours B empties 2 tanks every 6 hours C fills 1 tank every 6 hours Together, they empty 4 tanks every 6 hours So they empty 1 tank every 6/4 hours, and empty half of a tank in 3/4 hours. C. _________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

Re: PS: Pool fills [#permalink]
16 Aug 2009, 11:09

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12.At their respective rates, pump A, B, and C can fulfill an empty tank, or pump-out the full tank in 2, 3, and 6 hours. If A and B are used to pump-out water from the half-full tank, while C is used to fill water into the tank, in how many hours, the tank will be empty? A. 2/3 B. 1 C. 3/4 D. 3/2 E. 2

Re: PS: Pool fills [#permalink]
17 Aug 2009, 21:46

IanStewart wrote:

You can use a rates formula here, or convert each worker to the same amount of time (6 hours) :

A empties 3 tanks every 6 hours B empties 2 tanks every 6 hours C fills 1 tank every 6 hours Together, they empty 4 tanks every 6 hours So they empty 1 tank every 6/4 hours, and empty half of a tank in 3/4 hours. C.

Re: PS: Pool fills [#permalink]
17 Aug 2009, 22:17

Quote:

You can use a rates formula here, or convert each worker to the same amount of time (6 hours) :

A empties 3 tanks every 6 hours B empties 2 tanks every 6 hours C fills 1 tank every 6 hours Together, they empty 4 tanks every 6 hours So they empty 1 tank every 6/4 hours, and empty half of a tank in 3/4 hours. C.

Good job Ian. You made it all simple. _________________

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Re: PS: Pool fills [#permalink]
28 Sep 2013, 09:53

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Rate(A)=1/2 Rate(B)=1/3 Rate(C)=1/6

A + B - C

1/2 + 1/3 - 1/6 = 4/6 (Combined rate per the question)

Rate * Time = Work

4/6 * Time = 1/2

Time = 3/4 _________________

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Re: PS: Pool fills [#permalink]
17 Oct 2013, 02:53

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Expert's post

rrsnathan wrote:

TGC wrote:

Rate(A)=1/2 Rate(B)=1/3 Rate(C)=1/6

A + B - C

1/2 + 1/3 - 1/6 = 4/6 (Combined rate per the question)

Rate * Time = Work

4/6 * Time = 1/2

Time = 3/4

Hi,

I could understand this method. But my doubt is Work = Rate * time Time = Work / Rate

So as per this problem Rate(A)=1/2 Rate(B)=1/3 Rate(C)=1/6

So total time is: (1/2)/(1/2) + (1/2) / (1/3) - (1/2) / (1/6) = -1/2

Where iam missing something?? Please help me

thanks, Rrsnathan.

When adding rates you get combined rate not time. Also, why are you multiplying combined rate by 1/2?

At their respective rates, pump A, B, and C can fulfill an empty tank, or pump-out the full tank in 2, 3, and 6 hours. If A and B are used to pump-out water from the half-full tank, while C is used to fill water into the tank, in how many hours, the tank will be empty? A. 2/3 B. 1 C. 3/4 D. 3/2 E. 2

Rate of A = 1/2 tank/hour; Rate of B = 1/3 tank/hour; Rate of C = 1/6 tank/hour.

Combined rate when A and B are used to pump-out water, while C is used to fill water into the tank is 1/2+1/3-1/6=2/3 tank hour.

So, to empty the full tank 3/2 hours (reciprocal of rate) are needed. To empty the half-full tank half of that time would be needed: 1/2*3/2=3/4 hours.

Re: At their respective rates, pump A, B, and C can fulfill an [#permalink]
18 Apr 2015, 12:57

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