Management Aptitude Test Sep 2013 Paper

Question : 81 of 200

Marks: +1, -0

Pipe A can fill an empty tank in 30 h while pipe B can fill it in 45 h. Pipe A and B are opened and closed alternatively, i.e., first pipe A is opened, then B, again A and then B and so on for 1 h each time without any time lapse. In how many hours will the tank be filled when it was empty, initially ?

36 h
54 h
48 h
60 h

Validate

Solution:

(a) Part of tank filled by pipe A in 1 h = 1 /30
Part of tank filled by pipe B in 1 h = 1/45
Then, part of tank filled in 2 h when one pipe is opened at a time
=

1/30+1/45={3+2}/90

5/90=1/18

Now, let the tank takes x h to get filled.
Then,

1/18×x

= 1
x = 18 h
Also,

1/18

part is filled in 2 h
∴Tank is filled in 2x h = 2 × 18 = 36 h

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