a cistern normally takes 6 hours to be filled by a tap but because of a leak , 2 hours more . in how many hours will the leak empty a full cistern ?
∵ cistern fill in 6 hours . ∴ in 1 hour , filled part = 1 ⁄ 6 th now , due to leakage , filled part in 1 hour = 1 ⁄ 8 th part of the cistern emptied , due to leakage in 1 hour = 1 ⁄ 6 - 1 ⁄ 8 = 1 ⁄ 24 th ∴ the leakage will empty the full cistern in 24 hrs . answer b
inverse(subtract(inverse(6), inverse(add(2, 6))))