If pipes A and B can fill a tank in 36 hours and 48 hours respectively. Both pipes are opened together for 9 hours and then A is closed. Pipe B alone will fill the remaining part of the tank now in?

27 hours

(A + B) fill the tank in 9 hours = 7 × 9 = 63

Remaining = 144 - 63 = 81

B will fill remaining tank in = \(\frac{81}{3}\) = 27 hours