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Euler question:

  1. Oct 12, 2005 #1
    Hi

    I'm told that the following can be viewed as a an euler problem:

    If a farmer goes to marked and wants to buy chickens and cows for 2000 dollars.

    One chicken costs 20 dollars and one cow 10 dollars. How many chickens and cows does that farmer buy ?

    Is it [tex]x^{20} + y^{10} \equiv 2000[/tex] ???

    if yes how do I solve it ?

    /Bob
     
  2. jcsd
  3. Oct 12, 2005 #2

    TD

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    Homework Helper

    If a chicken costs 20 and you represent the number of chickens by x, the cost would be 20x instead of x^20, no? Same for the cows, I don't see why you introduced powers here.

    Edit: bit too late :smile:
     
  4. Oct 12, 2005 #3
    Okay it is then
    [tex]20x + 10y = 2000[/tex] ???
     
    Last edited: Oct 12, 2005
  5. Oct 12, 2005 #4

    TD

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    That seems more logical, yes :smile:
     
  6. Jul 21, 2008 #5
    Since there hasn't been a solution, I'll post one for those who are interested.

    Let x be the number of chickens which the farmer buys.
    Let y be the number of cows which the farmer buys.

    Therefore,
    20x + 10y = 2000
    2x + y = 200

    2x= 200-y .... (1)
    x= (200-y)/2 = 100 - y/2

    Since x is an integer and 100, is an integer.
    Therefore y/2 must be an integer.

    Let y= 2a, where a is any integer.

    Substitute y=2a into (1):
    2x= 200 - 2a
    x = 100-a

    General solutions are:
    x=100-a .... (2)
    y=2a .... (3)
    -----------------------------------------------
    For positive integer solutions:

    Let x = 100-a > 0, a< 100
    Let y = 2a > 0, a>0

    Therefore a can have any integer value between 1 - 99 inclusive.
    -----------------------------------------------------
    To find 1 solution, substitute one value of a into (2) and (3): (For example, use a =1 )
    x = 100 - a = 100- 1 = 99
    y = 2a = 2(1) = 2

    One solution for this question would be:
    The farmer buys 99 chickens and 2 cows.
     
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