SOLUTION: outt of three pipes Ist and 2nd opened opened tank filled in 12 mts Ist and IIIrd took 20 mts. How much time takes if all three are opened?

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Question 550049: outt of three pipes Ist and 2nd opened opened tank filled in 12 mts Ist and IIIrd took 20 mts. How much time takes if all three are opened?



Answer by mathstutor458(57) About Me  (Show Source):
You can put this solution on YOUR website!
1st and 2nd pipes fills the tank in 12mts.So, the work done by 1st and 2nd pipes are 1/12.
3rd pipe took 20mts.So,work done by 3rd pipe in one mt is 1/20.
if all three are opened together then work done in 1mt=1/12 + 1/20=2/15
Time=1/workdone in 1mt(here)
Therefore, time taken=1/(2/15)=15/2= 7 1/2