A cistern has two taps which fill it in 12 min. and 15 min.respectively There is one outlet pipe in the cistern. When all the taps & pipe are opened, the empty cistern is full in 20 min. How long will the waste pipe (outlet) take to empty the full cistern?
Q1. A cistern has two taps which fill it in 12 min. and 15 min.respectively There is one outlet pipe in the cistern. When all the taps & pipe are opened, the empty cistern is full in 20 min. How long will the waste pipe (outlet) take to empty the full cistern?
Answer: 10 min
Explanation: Net fill rate with both taps open = 1/12 + 1/15 = 3/20 per min; in 20 min it fills 3 tanks but only 1 is needed, so the outlet drains 2 tanks in 20 min → empties 1 tank in 10 min.