Practice Test Discussion


Three pipes A, B and C can fill a tank in 6 hours. After three pipes worked for 2 hours C is closed. Then A and B filled the remaining part in 7 hours. calculate the number of hours taken by C alone to fill the tank is?

  • Explanation

    The capacity of the tank can be obtained by finding LCM of 6, 2 and 7 which is 42.

    Total parts of the tank is 42

    A, B, C together can fill the tank in 6 hours

    42 parts6 hours=7 parts1 hour

    A,B and C can fill 7 parts in 1 hour

    From the question A, B and C together are filling only for 2 hours

    =14 parts2 hour

    Together they complete 14 parts in 2 hours

    And the remaining 28 part will be filled by A and B in 7 hours

    28 parts7 hours=4 parts1 hour

    A and B together can fill 4 parts in 1 hour

    From this we could find C’s filling parts per hour
    (A+B+C)-( A+B)=C

    7-4= 3 parts

    Total 42 parts of the tank will be filled by C alone

    423=14 hours

    Hence option D is correct.

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    Pipes and cisterns

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