SOLUTION: out of four pipes when 1,2,3 pipes are opened tank filled in 12 minutes; when 2,3,4 pipes opened time taken is 15 minutes;when 1 and 2 are opened it taken 20 minutes. How much time

Algebra ->  Equations -> SOLUTION: out of four pipes when 1,2,3 pipes are opened tank filled in 12 minutes; when 2,3,4 pipes opened time taken is 15 minutes;when 1 and 2 are opened it taken 20 minutes. How much time      Log On


   

Question 550035: out of four pipes when 1,2,3 pipes are opened tank filled in 12 minutes; when 2,3,4 pipes opened time taken is 15 minutes;when 1 and 2 are opened it taken 20 minutes. How much time will take when all the four pipes are opened?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The pipes are assumed to fill tank at different rates
Let r%5B1%5D = rate for pipe 1
Let r%5B2%5D = rate for pipe 2
Let r%5B3%5D = rate for pipe 3
Let r%5B4%5D = rate for pipe 4
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given:
(1) +r%5B1%5D+%2B+r%5B2%5D+%2B+r%5B3%5D+=+1%2F12+
(2) +r%5B2%5D+%2B+r%5B3%5D+%2B+r%5B4%5D+=+1%2F15+
(3) +r%5B1%5D+%2B+r%5B2%5D+=+1%2F20+
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Substitute (3) into (1)
(1) +1%2F20+%2B+r%5B3%5D+=+1%2F12+
(1) +r%5B3%5D+=+1%2F12+-+1%2F20+
(1) +r%5B3%5D+=+5%2F60+-+3%2F60+
(1) +r%5B3%5D+=+1%2F30+
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This is 4 unknowns and only 3 equations.
Is some data missing?
I don't think this can be solved