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Math Help - ferterliser in paddock problem

  1. #1
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    ferterliser in paddock problem

    A farmer needs to spread fertiliser over a paddock measuring 40 m by 80 m. The instructions on the fertiliser bag say to use 80 grams per square metre. How many kilograms of fertiliser will be needed?

    I did 80 divied by 1000 = 0.08 kg is that right?
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  2. #2
    Senior Member eumyang's Avatar
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    All you did was convert 80 g to kg. But 0.08 kg of fertilizer is supposed to be used for 1 square meter. But the paddock is not 1 square meter, is it? How do we find out the area of this paddock?
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  3. #3
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    would it be 40m x 80m = 3200/ 1000 = 3.2 kg
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  4. #4
    Senior Member eumyang's Avatar
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    No, that's not right. You got the area, 3200\,\text{m}^2. Why on earth would you try to convert to kg by dividing by 1000? Can't do that, my friend.

    We have a proportion here. If 0.08 kg is used for 1\,\text{m}^2, how many kilograms is used for 3200\,\text{m}^2? You could set up the proportion like this:
    \dfrac{0.08}{1} = \dfrac{x}{3200}
    ... and solve for x.
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  5. #5
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    would 0.08 x 3200 = 256 kg for 3200 be correct
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  6. #6
    Senior Member eumyang's Avatar
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    Yes, it is 256 kg.
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