Banking Quantitative Aptitude Sample Paper Quantitative Aptitude Sample Paper-11

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?    [FCI (Assistant) Grade III 2015]

A) 12 min 40 s

B) 11 min 35 s

C) 14 min 40 s

D) 13 min 35 s

Correct Answer: C

Solution :

Part filled by both in 1 min

\[=\frac{1}{15}+\frac{1}{20}=\frac{4+3}{60}=\frac{7}{60}\]

Now, part filled in 4 min \[=4\times \frac{7}{60}=\frac{7}{15}\]

\[\therefore \] Remaining part \[=1-\frac{7}{15}=\frac{8}{15}\]

Now, let the remaining part is filled by pipe B in x min.

Then, \[x\times \frac{1}{20}=\frac{8}{15}\]

\[\Rightarrow \] \[x=\frac{8\times 20}{15}=\frac{8\times 4}{3}\]

\[\Rightarrow \] \[x=\frac{32}{3}=10\frac{2}{3}=\left( 10+\frac{2}{3} \right)\min \]

\[\Rightarrow \] \[x=10+\frac{2}{3}\times 60\]

\[x=10\min \,+40\,\,=\,10\min 40\,s\]

\[\therefore \] Total time taken to fill tank

\[=4\min +10\min 40\,s\]

\[=14\min 40\,s\]