Two pipes X and Y fill a tank in 15 hrs. and 20 hrs. respectively, while a third pipe 'Z' can empty the full tank in 25 hrs. All the three pipes are opened in the beginning. After 10 hrs. Z is closed. In how much time, will the tank be full?
Q1. Two pipes X and Y fill a tank in 15 hrs. and 20 hrs. respectively, while a third pipe 'Z' can empty the full tank in 25 hrs. All the three pipes are opened in the beginning. After 10 hrs. Z is closed. In how much time, will the tank be full?
Answer: 12 hrs
Explanation: In 10 hours all three pipes fill 23/30 of the tank; the remaining 7/30 is filled by X and Y alone (rate 7/60 per hour) in 2 more hours, totalling 12 hours.