a can fill tank in 9 minutes , b can empty the tank in 18 minutes . . in what time the tank be filled , if both pipes work simultaneously ?
bigger no = 18 , ratio = 9 : 18 = 1 : 2 time taken to fill the tank = 18 / ( 2 - 1 ) = 18 minutes answer : e
divide(const_1, subtract(divide(const_1, 9), divide(const_1, 18)))