Three pipes $A,B$ and $C$ can fill a tank in $6$ hours After working at it together for $2$ hours , $C$ is closed and $A$ and $B$ can fill the remaining part in $7$ hours. The number of hours taken by $C$ alone to fill the tank is :

Q. Three pipes P, Q and R can fill a tank in 12 hours. After working at it together for 4 hours, R is closed. P and Q can fill the remaining tank in 14 hours. What is the number of hours taken by R alone to fill the tank?

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Three pipes P, Q and R can fill a tank in 12 hours. After working at it together for 4 hours, R is closed. P and Q can fill the remaining tank in 14 hours. What is the number of hours taken by R alone to fill the tank?

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Three ducts M, N and P can fill a tank in 18 hours. After working at it together for 6 hours, P is closed and M and N can fill the remaining part in 21 hours. The number of hours taken by P alone to fill the reservoir is:

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Three ducts M, N and P can fill a tank in 18 hours. After working at it together for 6 hours, P is closed and M and N can fill the remaining part in 21 hours. The number of hours taken by P alone to fill the reservoir is:

Q. Pipe A can fill a tank in 120 hours and pipe B can fill the same tank in 12 hours. Both the pipes are opened to fill the tank and after 3 hours pipe $A$ is closed. In how many hours the pipe B will fill the remaining part of the tank.