Indian Institute of Foreign Trade 2015 Solved Paper

Question : 8 of 124

Marks: +1, -0

A tank is connected with both inlet pipes and outlet pipes. Individually, an inlet pipe can fill the tank in 7 hours and an outlet pipe can empty it in 5 hours. If all the pipes are kept open, it takes exactly 7 hours far a completely filled-in tank to empty. If the total number of pipes, connected to the tank is 11, how many of these an inlet pipes?

Validate

Solution:

(d) Let there be 'x' inlet pipes
∴outlet pipes = (11 – x)
Now, According to question

{ x } /{ 7 } - { ( 11 - x ) }/ { 5 } = - 1 / 7

{ 5 x - 77 + 7 x }/ { 35 } = - 1 / 7

12 x = 72

x = 6

∴ Number of inlet pipes = 6

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