Pipe A and B can fill a tank in 12 h and 18 h, respectively, whereas Pipe C can empty the full tank in 8 h, A and B are opened for h and then closed. C alone will empty the tank in (in h)
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e. 5.
Given:
Pipe A and B can fill a tank in 12 h and 18 h,
Whereas Pipe C can empty the full tank in 8 h.
A and B are opened for h and then closed
Calculations:
Total work (LCM of 12, 18 and 8) = 72 units
Efficiency of A (72/12) = 6 units
Efficiency of B (72/18) = 4 units
Efficiency of C (72/8) = 9 units (Negative)
Efficiency of A and B (6 + 4) = 10 units
Work done in hours = 10 × 9/2 = 45 units
Required time taken by C = 45/9 = 5 hours