Management Aptitude Test Dec 2012 Paper

Question : 114 of 200

Marks: +1, -0

A bath can be filled by the cold water and hot water pipes in 10 min and 15 min, respectively. A person leaves the bathroom after turning on both pipes simultaneously and returns at the moment when the bath should be full. Finding however, that the waste pipe has been open, he then closes it. In exactly four minutes more the bath is fill. In how much time would the waste pipe empty the full bath, if it alone is opened?

9 min
10 min
12 min
None of these

Validate

Solution:

(d) Time taken by cold water and hot water pipes to fill the both
=

{10×15} /{10+15}= {10×15}/25

= 6 min
Thus, when the waste pipe is also open, then time taken to fill the bath
= 6 + 4 = 10 min
Now, let waste pipe can empty the full bath in x min,
Then,

1/10+1/15-1/x=1/10

⇒

1/x=1/15

⇒ x = 15 min

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