Quantitative Aptitude Ques 59
Question: 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]
Options:
A) 12 min 40 s
B) 11 min 35 s
C) 14 min 40 s
D) 13 min 35 s
Show Answer
Answer:
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}=( 10+\frac{2}{3} )\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 $
BETA
