Q. Two pipes fill a tank in 30 hours and 40 hours. If both are opened together for 10 hours and then the slower pipe is closed, how long will the faster pipe take to fill the remaining tank?
✅ Correct Answer: (B)
12 hours
Explanation: Work in 10 hrs = 7/120 → remaining = 113/120 → faster pipe (1/30) takes ≈12 hrs.
Explanation by: Hriday
Work in 10 hrs = 7/120 → remaining = 113/120 → faster pipe (1/30) takes ≈12 hrs.