pipes a and b can fill a tank in 3 and 4 hours . pipe c can empty it in 4 hours . if all pipes are opened together , then the tank will be filled in ?
"net part filled in 1 hour = 1 / 3 + 1 / 4 - 1 / 4 = 1 / 3 the tank will be full in 3 hr answer is a"
inverse(subtract(add(divide(const_1, 3), divide(const_1, 4)), divide(const_1, 4)))