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# Pumps A,B and C operate at their respective speeds. Pumps A

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Pumps A,B and C operate at their respective speeds. Pumps A [#permalink]

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04 Jan 2006, 14:38
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Pumps A,B and C operate at their respective speeds. Pumps A and B operating simultaneously can fill the tank in 6/5 hrs, pumps A and C operating simultaneously can fill the tank in 3/2 hrs and pumps B and C operating simultaneously can fill the tank in 2 hrs. How long does it take pumps A,B and C working simultaneously to fill the tank?

a) 1/3

b) 1/2

c) 2/3

d) 5/6

e) 1

************************************

To my recollecting in a 3 machine combined work problem, the formula is
t=ABC/(AB+BC+AC). The denominator terms are given in the problem but not the numerator...how do I solve this problem? I am sure I am missing something pretty stupid.
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04 Jan 2006, 14:43
Ignore my request. I found out. As I had thought I missed something stupid. You can solve it if you want to...
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05 Jan 2006, 13:22
plsubbu...can u post ur workings ????

thanx
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05 Jan 2006, 14:29

1/a + 1/b = 5/6
1/a + 1/c = 2/3
1/b + 1/c = 1/2

2(1/a+1/b+1/c) = 5/6 + 2/3 + 1/2
1/a+1/b+1/c = 1/t
so 2(1/t) = 5/6 + 2/3 + 1/2
which is 1/t = 1
i.e t = 1.
here is my take..   [#permalink] 05 Jan 2006, 14:29
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