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Math Help - Word problem help!

  1. #1
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    Word problem help!

    Bob is buying mulch for a right-triangular garden with legs of measure 10ft and 26ft. When the mulch is uniformly spread 2 inches deep, each bag of mulch will cover 12 sq ft. Bob plans to uniformly spread his mulch 3 inches deep. What is the closest value to the number of bags of mulch Bob will need for the garden?

    How does one obtain the answer 17??
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  2. #2
    MHF Contributor ebaines's Avatar
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    Re: Word problem help!

    First calculate the area of the garden, using the formula for area of a triangle: A=(1/2)bh. For a right-angle triangle the length of the base (b) and height (h) are the same as the two legs. Divide the area by 12 to find how many bags are needed for 2" deep mulch. Then multiply that by 3/2 so that the depth is increased from 2 to 3 inches. If you end up with an answer that is not a whole number round up to the next whole number. This should give the answer of 17.
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  3. #3
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    Re: Word problem help!

    Mathematically it works, but I'm still not seeing why to mutiply by 3/2..
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  4. #4
    MHF Contributor ebaines's Avatar
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    Re: Word problem help!

    Dividing the area by 12 gives you the number of bags of mulch for a depth of 2 inches - right? The total volume of mulch needed to get a depth of 3 inches instead of 2 inches is 3/2 of that, because you are increasing the depth by a factor of 3/2. If you wanted 5 inches of depth you woukd multiply by 5/2. If you want only 1 inch of depth you would multiply by 1/2.
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