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Work word probem

  1. Jun 24, 2013 #1
    1. The problem statement, all variables and given/known data

    A contractor employed a certain number of men to complete a work in a certain number of days. If 3 more men were deployed the work would be finished 2 days earlier while
    if 12 more men were deployed it would be finished 5 days earlier. Find number of men
    deployed by the contractor.


    2. Relevant equations



    3. The attempt at a solution
    Let the number of men be n. Let the number of days be t.
    Now how should I translate this problem into equation ? Please help!
     
  2. jcsd
  3. Jun 24, 2013 #2

    Office_Shredder

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    If the job needs M man-days of work to be completed, then
    n*t = M

    Can you use the information given to write down two more equations that involve n, t, and M?
     
  4. Jun 24, 2013 #3

    verty

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    These problems are nasty, the type that I hate the most, needing one to use variables and needing simultaneous equations to solve.

    Think of units of work: 1 worker working for 1 day does 1 unit of work. Units of work per day is how we measure how productive a team is. Now let M be the number of units of work required to complete the project. This is exactly in line with what Office_Shredder said.
     
  5. Jun 25, 2013 #4
    Yes.
    n*t=M
    Also (n+3)(t-2)=M and (n+12)(t-5)=m
    And ... I just solved this simultaneous equations to get n=12 and t=10 which is the correct answer.
    Thanks a lot for help!
     
  6. Jun 25, 2013 #5

    HallsofIvy

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    In other words, all of algebra?

     
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