three pipes a , b and c can fill a tank from empty to full in 20 minutes , 20 minutes and 30 minutes respectively . when the tank is empty , all the three pipes are opened . a , b and c discharge chemical solutions p , q and r respectively . what is the proportion of solution r in the liquid in the tank after 3 minutes ?
part filled by ( a + b + c ) in 3 minutes = 3 ( 1 / 20 + 1 / 20 + 1 / 30 ) = 6 / 15 part filled by c in 3 minutes = 3 / 30 required ratio = 3 / 30 * 15 / 6 = 1 / 4 answer : d
multiply(divide(3, 30), divide(const_1, multiply(3, add(divide(const_1, 30), add(divide(const_1, 20), divide(const_1, 20))))))