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Ratio Question with 3 quantities

  1. Aug 12, 2016 #1
    1. The problem statement, all variables and given/known data
    If 15 workers can pave 18 driveways in 24 days, how many days would it take 40 workers to pave 22 driveways

    2. Relevant equations
    Actually i dont know which equation should be used for 3 quantities. I know the eq for two quantities.
    Because we increasing labours so we would require less days
    Workers * days/ increased workers (i.e constant product eq)

    3. The attempt at a solution

    I can find days using above eq:

    15 * 24/40 = 9 days
    For 18 drive ways we need 9 days
    For 1 drive way , we would need 18/9 = 2 days
    For 22 driveways, we would need 11 days.

    Is there a simple method for solving the above problem.

    Zulfi.
     
  2. jcsd
  3. Aug 12, 2016 #2

    haruspex

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    Think about the work needed per driveway.
     
  4. Aug 12, 2016 #3

    Ray Vickson

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    Your method is OK in this case. In general, however, it is helpful to introduce an algebraic symbol; for example, in this case you can let ##p## be the number of driveways paved per day for 1 worker. Thus, 15 workers can pave ##15p## driveways per day, or ## 15 p \times 24## driveways in 24 days.
     
  5. Aug 13, 2016 #4
    Hi,
    Can some body guide me why the output of following is in terms of days?
    15 * 24/40 = 9 days
    Zulfi.
     
  6. Aug 13, 2016 #5

    haruspex

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    What are the units for the three inputs, the 15, the 24 and the 40?
     
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