Three Pipes P,Q and R can fill a tank in 6 hours. After working all three together for 2 hours. R is closed and P and Q can fill the remaining part in 7 hours.The number of hours taken by R alone to fill the tank is ?

A 10

B 12

C 14

D 16

Solution

Correct Answer: Option C

Solution:

In 2 hours P,Q and R can fill = 2/6 = 1/3 part.

Remaining part = 1 - 1/3 = 2/3

2/3 part filled by P and Q in = 7 hours.

So, 1 part is filled by P and Q in \(7 \times \frac{3}{2} = \frac{{21}}{2}\) hours.

So, R alone can fill = 1/6 - 2/21 = (7-4)/42 = 3/42 = 1/14 part

So, R alone can fill the tank in = 14 hours.

Solution

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