Pipes A, B and C together can fill a tank in 4 hours. Pipes A and B together can fill the tank in 9 hours. If pipes A, B and C are opened simultaneously, and after 3 hours, pipes A and B are closed, then how many hours will C alone require to fill the tank?
A and B works for 3 hours , so remaining work =36-3$$\times\ 9$$=9
so C alon can fill the tank in $$\ \frac{\ 9}{5}=1.8\ hours$$,
hence option 'D' is correct.
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