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Math Help - story problem

  1. #1
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    story problem

    I'm horrible with story problems but this one just kind of confuses me with the wording its something I found on the net can anyone help?


    A man has a miniature Pyramid of Egypt. It is 3 inches in height. The man was invited to display it at an exhibition. He felt it was too small and decided to build a scaled-up model of the Pyramid out of material whose density is (1/8) times the density of the material used for the miniature. He did a "back-of-the-envelope" calculation to check whether the model would be big enough.

    If the mass (or weight) of the miniature and the scaled-up model are to be the same, how many inches in height will the scaled-up Pyramid? Give your answer to two places of decimal.
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  2. #2
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    Quote Originally Posted by flyingsilverschoo View Post
    I'm horrible with story problems but this one just kind of confuses me with the wording its something I found on the net can anyone help?


    A man has a miniature Pyramid of Egypt. It is 3 inches in height. The man was invited to display it at an exhibition. He felt it was too small and decided to build a scaled-up model of the Pyramid out of material whose density is (1/8) times the density of the material used for the miniature. He did a "back-of-the-envelope" calculation to check whether the model would be big enough.

    If the mass (or weight) of the miniature and the scaled-up model are to be the same, how many inches in height will the scaled-up Pyramid? Give your answer to two places of decimal.
    Assume the pyramid is solid. Then if the linear measurements are scaled by
    a factor lambda, then the volume is scaled by lambda^3.

    So let the scale factor be lambda.

    For the masses to be the same if the large pyramid has a density 1/8
    of the small, then the volume of the larger must be 8 times that of the
    smaller. So lambda^3=8, and so lambda=2.

    Hence the height of the scaled up pyramid will be 6 inches.

    RonL
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  3. #3
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    thanks I was just starting to think it would be 24inches because multiply by 8 so thanks
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