SSC CGL – Combined Graduate Level Examination · Question 68
Three pipes, A, B, and C are capable of filling a tank in 6, 8, and 12 hours, respectively. When all three pipes are opened together, they operate for 2 hours before pipe C is closed. How much additional time will it take to completely fill the tank after that?
Show answer & explanation
Answer: (A) 6/7 hours
Explanation
In 2 hours all three fill 2 × (1/6 + 1/8 + 1/12) = 3/4. The remaining 1/4 at A + B's rate of 7/24 per hour takes 6/7 hours. (Verified against the official SSC answer key.)