RRB ALP 2013 Ques 81
Question: Two pipes can fill a tank with water in 15 and 12 hours respectively and a third pipe can empty it in 4 hours. If the pipes be opened in order, at 8, 9 and 11 a.m. respectively, the tank will be emptied at:
Options:
A) 11:40 a.m.
B) 12:40 p.m.
C) 1:40 p.m.
D) 2:40 p.m.
Show Answer
Answer:
Correct Answer: D
Solution:
- Let the tank will be emptied at $ x $ a.m. Tank filled by first pipe $ =\frac{1}{15}\times (x-8) $ Tank filled by second pipe $ =\frac{1}{12}\times (x-9) $ and tank emptied by third pipe $ =\frac{1}{4}\times (x-1) $
$ \therefore $ $ \frac{x-8}{15}+\frac{x-9}{12}=\frac{x-11}{4} $
$ \Rightarrow $ $ \frac{4x-32+5x-45}{60}=\frac{x-11}{4} $
$ \Rightarrow $ $ 9x-77=15x-165 $
$ \Rightarrow $ $ 6x=88 $
$ \therefore $ $ x=\frac{88}{6}=14\frac{2}{3} $ i.e. 2:40 p.m.
BETA
