pipe p can fill a tank in 6 hours , pipe q in 12 hours and pipe r in 24 hours . if all the pipes are open , in how many hours will the tank be filled ?
"explanation : part filled by ( p + q + r ) in 1 hour = ( 1 / 6 + 1 / 12 + 1 / 24 ) = 7 / 24 all the three pipes together will fill the tank = 24 / 7 = 3.4 hours answer d"
inverse(add(divide(const_1, 24), add(divide(const_1, 6), divide(const_1, 12))))