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?\nOptions:\n(A) 1/2\n(B) 1/5\n(C) 1/3\n(D) 1/4\n(E) 1/6 Stream of consciousness:
User
Part filled by (A + B + C) in 3 minutes = 3(1/20 + 1/20 + 1/30) = 6/15\nPart filled by C in 3 minutes = 3/30\nRequired ratio = 3/30 * 15/6 = 1/4
Thus, the answer is (D).
Assistant