Chicken food riddle


Farmer John has a chicken farm. On a certain day, John calculates in how many days he will run out of chicken-food. He notices that if he would sell 75 of his chickens, he could feed the remaining chickens twenty days longer with the chicken-food he has, and that if he would buy 100 extra chickens, he would run out of chicken-food fifteen days earlier.

How many chickens does farmer John have?

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  • 2 Answer(s)


    Yodha Expert Answered on 4th November 2018.
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    Some explanation on the answer Yodha already gave.

    The product of the number of chickens and the number of days stays the same, which leads to the following calculations:

    C*D = (C-75)*(D+20) = (C+100)*(D-15)
    C*D = C*D+20C-75D-1500 = C*D-15C+100D-1500
    0 = 20C-75D-1500 = -15C+100D-1500

    60C = 225D+4500
    60C = 400D-6000

    225D+4500 = 400D-6000
    175D = 10500
    D = 10500/175 = 60
    C = 225 + 75
    = 400 – 100
    = 300

    CugelTheWise Expert Answered on 5th November 2018.

    could have upvote my answer xd

    on 5th November 2018.
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