SSC Sample Paper Mock Test-8 SSC CGL Tear-II Paper-1

Two pipes A and B can fill a tank in 15 min and 20 min, respectively. Both the pipes are opened together. But, after 4 min, pipe A is turned off. What is the total time required to fill the tank?

A)       10 min 20 s

B)        11 min 45 s

C) 12 min 30 s

D) 14 min 40 s

Correct Answer: D

Solution :

Part filled by both in 4 min \[=4\times \left( \frac{1}{15}+\frac{1}{20} \right)\]

\[=\left( 4\times \frac{7}{60} \right)=\frac{7}{15}\]

Pact unfilled \[=\left( 1-\frac{7}{15} \right)=\frac{8}{15}\]

\[\frac{1}{20}\]part is filled by B in 1 min

\[\frac{8}{15}\]part is filled by B in \[\left( 20\times \frac{8}{15} \right)\]min

\[=\frac{32}{3}\min =10\min 40\,\,s\]

Total time taken = (4 min +10 min 40 s) = 14 min 40 s