A cylinder water tank is 70cm in diameter. To being with, it is fullof water. A leak starts in the bottom so that it loses 10liters of water every hour. How long will it take for the water level to fall by 20cm

Answer 1

the missing water leaves an empty cylinder, of volume
v = πr^2 h = π * 35^2 * 20 = 24500π cm^3
so, dividing by the rate of depletion,
24500π cm^3 / (10000 cm^3/hr) = 2.45π = 7.69 hr