Two inlet pipes A and B can fill an empty cistern in 22 and 33 hours respectively. Both are opened together, but A is closed 3 hours before the cistern is full. In how many hours in total is the cistern filled?

1. Let total time be T. Then B works for T hours and A works for (T - 3) hours. 2. (T - 3)/22 + T/33 = 1; multiply by 66: 3(T - 3) + 2T = 66. 3. 5T - 9 = 66, so 5T = 75 and T = 15 hours. _Source: RRB Group D CEN-02/2018 PYQ, Q.99._