Question

Three pipes A, B and C can fill a tank from empty to full in 30 minutes, 20 minutes, and 10 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 the solution R in the liquid in the tank after 3 minutes?

• A. $\frac{5}{11}$
  
• B. $\frac{6}{11}$
  
• C. $\frac{7}{11}$
  
• D. $\frac{8}{11}$

Answer 1

The correct option is B

$\frac{6}{11}$

Part filled by (A+B+C) in 3 minutes

$3(\frac{1}{30}+\frac{1}{20}+\frac{1}{10})=(3\times \frac{11}{60})=\frac{11}{20}$

Part filled by C in 3 minutes = $\frac{3}{10}$

$\therefore$ Required ratio = $(\frac{3}{10}3\times \frac{20}{11})=\frac{6}{11}$