Pipes and Cisterns Practice Test 1 with solutions

Question : 33 of 40

Marks: +1, -0

A cistern is connected with three pipes A, B and C, where A and C are inlet pipes and B is an outlet pipe. Pipes A, B and C alone can fill the cistern in 15, 20 and 10 minutes respectively. Pipes A and B were opened for 10 minutes, then Pipe B was closed and Pipe C was connected along with Pipe A to fill the cistern. Find the time taken by Pipe A and C to fill the remaining part of the cistern.

5 minutes
10 minutes
15 minutes
20 minutes
Cannot be determined

Validate

Solution:

Part of cistern filled by A and B in 10 minutes
=

(1/{15}-1/{20})

× 10 =

({4-3}/{60})

× 10 =

1/6

Remaining portion that is to be filled = 1 -

1/6

5/6

Part of cistern filled by A and C in 1 minute
=

1/{15}+1/{10}

{2+3}/{30}

1/6

Time taken to fill

1/6

th part the of cistern = 1 minute
Time taken to fill

5/6

th part of the cistern = 1 × 5 = 5 minutes

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