A cistern is filled by a tap in 3 1/2 hours. Due to leak in the bottom of the cistern, it takes half an hour longer to fill the cistern. If the cistern is full how long will it take the leak to empty it?
Q1. A cistern is filled by a tap in 3 1/2 hours. Due to leak in the bottom of the cistern, it takes half an hour longer to fill the cistern. If the cistern is full how long will it take the leak to empty it?
Answer: 28 hours
Explanation: Tap fills in 3.5 hours; with leak it takes 4 hours: 1/4 = 1/3.5 - 1/L → 1/L = 1/3.5-1/4 = (4-3.5)/14 = 0.5/14 = 1/28; leak empties in 28 hours.