A pipe can fill an empty tank in 10 hours. Another pipe can empty a full tank…
2026
A pipe can fill an empty tank in 10 hours. Another pipe can empty a full tank in 40 hours. If both pipes are opened together when the tank is empty, how many hours will it take to fill (3/4) of the tank?
- A.
40
- B.
30
- C.
20
- D.
10
Attempted by 12 students.
Show answer & explanation
Correct answer: D
Step 1: Calculate the individual rates.
Filling rate = 1/10 of the tank per hour.
Emptying rate = 1/40 of the tank per hour.
Step 2: Calculate the net filling rate.
Subtract the emptying rate from the filling rate:
Net rate = (1/10) - (1/40) = (4/40) - (1/40) = 3/40 tank per hour.
Step 3: Calculate the time to fill 3/4 of the tank.
Divide the target work by the net rate:
Time = (3/4) / (3/40) = (3/4) × (40/3) = 10 hours.
Final Answer: Option 4