A pipe can fill a tank in 3 hours. There are two outlet pipes from the tank which can empty it in 7 and 10 hours respectively. If all the three pipes are opened simultaneously, then the tank will be filled in -

A. 8 hours

B. 9 hours

C. 10 hours

D. 11 hours

Answer: Option D

Solution(By Examveda Team)

Net part filled in 1 hour
$$\eqalign{ & {\text{ = }}\frac{1}{3} - \left( {\frac{1}{7} + \frac{1}{{10}}} \right) \cr & = \frac{1}{3} - \frac{{17}}{{70}} \cr & = \frac{{19}}{{210}} \cr} $$
∴ The tank will be filled in $$\frac{{210}}{{19}}$$  hours i.e.
$$\eqalign{ & {\text{= 11}}\frac{1}{{19}}{\text{ hours}} \cr & \cong 11\,{\text{hours }} \cr} $$