There are three pipes. In 30 minutes, 20 minutes, and 10 minutes, respectively, A, B, and C can fill a tank from empty to full. All three pipes are opened when the tank is empty. Chemical solutions P,Q, and R are discharged by A, B, and C, respectively. After 3 minutes, what is the proportion of solution R in the liquid in the tank?
A. 5/11
B. 6/11
C. 7/11
D. 8/11
Answer:B
There are three pipes. In 30 minutes, 20 minutes, and 10 minutes, respectively, A, B, and C can fill a tank from empty to full. All three pipes are opened when the tank is empty. Chemical solutions P,Q, and R are discharged by A, B, and C, respectively. After 3 minutes, what is the proportion of solution R in the liquid in the tank?
A. 5/11 B. 6/11 C. 7/11 D. 8/11
Explanation: Part completed in 3 minutes by (A + B + C) = 3 1/30+1/20+1/10 =3 x 11/60=11/20,C filled 3/10 of the part in 3 minutes.3/10 x 20/11 = 6/11 is the required ratio.