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Problem from the MBA.com practice test 1

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by pranavc » Thu Jul 03, 2008 7:56 pm
Pumps A, B, and C operate at their respective constant rates. Pumps A and B, operating simultaneously, can fill a certain takn in 6/5 hours; pumps A and C, operating simultaneously, can fill the tank in 3/2 hours; and pumps B and C, operating simultaneously, can fill the tank in 2 hours. How many hours does it take pumps A, B, and C, operating simultaneously, to fill the tank?

(A) 1/3
(B) 1/2
(C) 2/3
(D) 5/6
(E) 1

Any input on the above will be highly appreciated. Thanks in advance.
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Source: — Problem Solving |

by wawatan » Thu Jul 03, 2008 8:53 pm
let the total amount of work done be 120 units... therfore the amt of work done by a & b in one hr is 120/6/5= 100... a&c 120/3/2 = 80... b & c = 120/2 =60..... 2 ( a+b+c )= 240... a+b+c=120... the amt of work done in one hr by all three is 120 units... therefore working together they will take 1 hr...
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