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work problem

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rehab-299
 Post subject: work problem
 Post Posted: Sun Oct 25, 2009 3:11 pm 
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Students


Posts: 5
pump A can drain container in 3 hours, B can drain it in 2 hours and C can fill a full container in 6 hour opening A,B,C togather, if a container has full water, how many times does it drain the container will be half-full?

A)30 minutes
B) 45 minutes
C) 50 minutes
D) 60 mintes
E) 72 mintes
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2amitprakash
 Post subject: Re: work problem
 Post Posted: Sun Oct 25, 2009 4:06 pm 
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Course Students


Posts: 26
Find the rates for all 3:
Pump A will drain 1/3 of container in 1 hour
Pump B will drain 1/2 of container in 1 hour
Pump C will drain 1/6 of container in 1 hour.

So combined A+B+C will drain (1/3+1/2+1/6=1) container in 1 hour.

So 1/2 of container will be drained in 1/2 hour = 30 minutes. Answer is A.
Correct answer in later post. Earlier misread the problem


Last edited by 2amitprakash on Sun Oct 25, 2009 5:49 pm, edited 1 time in total.

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rehab-299
 Post subject: Re: work problem
 Post Posted: Sun Oct 25, 2009 4:16 pm 
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Posts: 5
the answer is B
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2amitprakash
 Post subject: Re: work problem
 Post Posted: Sun Oct 25, 2009 5:37 pm 
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Course Students


Posts: 26
Sorry to misread your problem in hurry...my bad. The logic remains same-
Find the rates for all 3:
Pump A will drain 1/3 of container in 1 hour
Pump B will drain 1/2 of container in 1 hour
Pump C will fill 1/6 of container in 1 hour.

So combined A+B+C will drain (1/3+1/2-1/6=4/6) container in 1 hour. Notice the negative sign for opposite action.

So 1/2 of container will be drained in [(1/2)*(6/4)] hours = 45 minutes. Answer is B.
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RonPurewal
 Post subject: Re: work problem
 Post Posted: Sat Jan 09, 2010 3:34 am 
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ManhattanGMAT Staff


Posts: 6765
2amitprakash wrote:
Sorry to misread your problem in hurry...my bad. The logic remains same-
Find the rates for all 3:
Pump A will drain 1/3 of container in 1 hour
Pump B will drain 1/2 of container in 1 hour
Pump C will fill 1/6 of container in 1 hour.

So combined A+B+C will drain (1/3+1/2-1/6=4/6) container in 1 hour. Notice the negative sign for opposite action.

So 1/2 of container will be drained in [(1/2)*(6/4)] hours = 45 minutes. Answer is B.


nicely done.
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