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Ratio and proportion

  1. Oct 12, 2009 #1
    If 100 bu of corn per acre remove 90lb of nitrogen, phosphorus, and potassium (N, P, and K, respectively), how many pounds of N, P, and K are removed by the yield of 135u per acre?


    I try to figure out how to starting to solve this problem but dont know how

    some help please
     
  2. jcsd
  3. Oct 12, 2009 #2

    Mark44

    Staff: Mentor

    This is hardly a "Calculus and Beyond" problem. A better place would be the Precalculus section.

    Wouldn't the ratio of 100 bu of corn to 90 lb N, P, and K be the same as the ratio of 135 lb corn to X lb of N, P, and K?

    Start with that.
     
  4. Oct 12, 2009 #3
    I am still confuse dont know how to start, the bu and lb are same thing?
     
  5. Oct 12, 2009 #4

    Mark44

    Staff: Mentor

    No, they're not. bu stands for bushel, a unit of volume, and lb stands for "pound", a unit of weight.

    Start by translating this sentence into an equation: Wouldn't the ratio of 100 bu of corn to 90 lb of fertilizer be the same as the ratio of 135 lb corn to X lb of fertilizer?
     
  6. Oct 13, 2009 #5
    ok here I got 100bu/90lb=135bu/xlb
    then I cross multiply
    90*135 = 12150/100
    = 121.5lb
    please advise me see if this is right

    thanks
     
  7. Oct 14, 2009 #6

    Mark44

    Staff: Mentor

    Yes.
    Where did x go? You started with an equation with x, and you should end up with an equation that has x = ...
     
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