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

Ques:- Three pipes X, Y and Z can fill a tank in 6 hours. After working at it together for 2 hours, Z is closed and X and Y can fill the remaining part in 7 hours. The number of hours taken by Z alone to fill the tank is:

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