Engineering Maths - Time and Work

36. A can finish a job in 12 days and B when working at twice his efficiency finishes a job in 9 days. How many days will they take if they work for two days alternately working at their standard rate given that A starts first?

  • Option : C
  • Explanation :
    A finishes the job at standard rate in 12 days.
    So in 1 day, the part of job done by A = 1/12
    Similarly the part of job done by B in 1 day

    So, in (2 alternate days work of 'A' and 'B')
    3 x 4 = 12 days
    They will finish 3 x (5/18) = 15/18 th of the work.
    Work remaining = 1 - (15/18) = 3/18 = 1/6
    This is finished by A alone in = 2 days.
    Hence, total number days = 12 + 2 = 14 days
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