Pipes A and B can fill a tank in 12 minutes and 15 minutes, respectively. The tank when fill can be emptied by pipe C in x minutes. When all the three pipes are opened simultaneously, the tank is full in 10 minutes. The value of x is:

Answer: Option C

Solution

Answer: Option C

Solution:

$$\begin{array}{rl}& A+B+C=\frac{60}{10}\\ & 5+4+C=6\\ & C=-3\\ & C\text{ can empty the tank }x\\ & =\frac{60}{3}=20\text{ minute}\end{array}$$