Pipes and Cisterns Practice Test 1 with solutions

Question : 38 of 40

Marks: +1, -0

Two pipes A and B can fill a tank in 15 minutes and 20 minutes respectively. Both the pipes are opened together but after 4 minutes, pipe A is turned off. The time required to fill the tank is:

14 min. 40 sec.
12 min. 30 sec.
11 min. 45 sec.
10 min. 20 sec.

Validate

Solution:

In 4 minutes the part filled by pipes (A + B) =

4(1/{15}+1/{20})

7/{15}

Remaining part = 1 –

7/{15}

8/{15}

Time taken by B to fill the remaining part =

{8/{15}}/{1/{20}}

{32}/3

min = 10 min. 40 sec.
Hence, total time taken = 4 min. + 10 min. 40 sec. = 14 min. 40 sec.

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