Pipe A alone can fill a tank in 8 hours. Pipe B alone can fill it in 6 hours.…
2023
Pipe A alone can fill a tank in 8 hours. Pipe B alone can fill it in 6 hours. If both the pipes are opened and after 2 hours pipe A is closed, then pipe B will fill the tank in :
- A.
2 hours
- B.
2½ hours
- C.
3 hours
- D.
3½ hours
Attempted by 12 students.
Show answer & explanation
Correct answer: B
Step-by-Step Solution
First, determine the work rates of each pipe.
Pipe A fills the tank in 8 hours, so its rate is 1/8 per hour.
Pipe B fills the tank in 6 hours, so its rate is 1/6 per hour.
Next, calculate the work done when both pipes are open for 2 hours.
Combined rate = 1/8 + 1/6 = 3/24 + 4/24 = 7/24 per hour.
Work done in 2 hours = 2 × (7/24) = 14/24 = 7/12 of the tank.
Now, find the remaining work to be done by Pipe B alone.
Remaining work = 1 - 7/12 = 5/12 of the tank.
Finally, calculate the time Pipe B takes to fill the remaining 5/12.
Time = (Remaining Work) / (Rate of B) = (5/12) / (1/6) = (5/12) × 6 = 30/12 = 2.5 hours.
Therefore, Pipe B will fill the remaining tank in 2.5 hours.