SSC Sample Paper Mock Test-5 SSC CGL Tear-II Paper-1

Two pipes X and Y can fill a tank in 36 min and 45 min respectively. A waste pipe Z can empty the tank in 30 min. First X and Y are opened. After 7 min, Z is also opened. In how much time, the tank is full?

A) 54 min

B) 64 min

C) 46 min

D) 36 min

Correct Answer: C

Solution :

Part filled in 7 min \[=7\times \left[ \frac{1}{36}\times \frac{1}{45} \right]=\frac{7}{20}\]

Remaining part \[=\left[ 1-\frac{7}{20} \right]=\frac{13}{20}\]

Part filled by \[(X+Y+Z)\] in 1 min

\[=\left[ \frac{1}{36}+\frac{1}{45}-\frac{1}{30} \right]=\frac{1}{60}\]

Now,\[\frac{1}{60}\]part is filled by them in 1 min

\[\therefore \]\[\frac{13}{20}\]part will be filled in\[\left[ \frac{60\times 13}{20} \right]=36\]min

\[\therefore \]Total time taken to fill the tank \[=(396+7)=46\] min