Time and Work


  1. 20 persons completed 1/3rd of the work in 12 days. How many more person are required to finish the rest work in next 12 days?









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    Work done = 1/3
    Remaining work = 2/3
    So for double work in same days we need double number of people i.e. 40.

    Correct Option: A

    Work done = 1/3
    Remaining work = 2/3
    So for double work in same days we need double number of people i.e. 40.

    So, 20 men will be increased.


  1. A and B can together do a piece of work in 15 days. B alone can do it 20 days. In how many days can A alone do it ?









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    A's 1 day's work = (1/15 - 1/20) = 1/60

    Correct Option: D

    A's 1 day's work = (1/15 - 1/20) = 1/60
    ∴ A alone can finish it in 60 days.



  1. A and B can do a piece of work in 6 days and A alone can do it in 9 days. The time taken by B alone to do the same work is ?









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    B's one day's work = (1/6 - 1/9) = 1/18

    Correct Option: A

    B's one day's work = (1/6 - 1/9) = 1/18
    ∴ B alone can finish it in 18 days.


  1. A and B can do a piece of work in 18 days, B and C in 24 days, A and C in 36 days. In what time can they do it all working together ?









  1. View Hint View Answer Discuss in Forum

    (A + B)'s 1 day's work = 1/18
    (B + C)'s 1 day's work = 1/24
    (A + C)'s 1 day's work = 1/36
    Adding 2 (A + B + C)'s 1 day's work = (1/18 + 1/24 + 1/36) = 1/8

    Correct Option: C

    (A + B)'s 1 day's work = 1/18
    (B + C)'s 1 day's work = 1/24
    (A + C)'s 1 day's work = 1/36
    Adding 2 (A + B + C)'s 1 day's work = (1/18 + 1/24 + 1/36) = 1/8
    ∴ (A + B + C)'s day's work = 1/16
    Hence, all working together can finish it in 16 days.



  1. A and B can do a piece of work in 12 days. B and C in 15 days. C and A in 20 days. A alone can do the work in ?









  1. View Hint View Answer Discuss in Forum

    ∵ [(A + B) + (B + C) + (C + A)]'s 1 day's work = (1/12 + 1/15 + 1/20) = 1/5
    ⇒ 2(A + B + C)'s 1 days work = 1/5
    ⇒ (A + B + C)'s 1 day's work = 1/10
    &rArr A's 1 day's work = (1/10 - 1/15) = 1/30
    ∴ A alone can finish it in 30 days.

    Correct Option: C

    ∵ [(A + B) + (B + C) + (C + A)]'s 1 day's work = (1/12 + 1/15 + 1/20) = 1/5
    ⇒ 2(A + B + C)'s 1 days work = 1/5
    ⇒ (A + B + C)'s 1 day's work = 1/10
    &rArr A's 1 day's work = (1/10 - 1/15) = 1/30
    ∴ A alone can finish it in 30 days.