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Geometry Question Help?

For a right circular cone the ratio of the slant height to the radius is 5:3 if the volume of the cone is 96 pie inches cubed. find the lateral area of the cone

the answer the book is giving me is 60pie

i can't see the pattern to solving this, can anyone give me step by step instructions.

1 Answer

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    V = (1/3) * pi * r^2 * h

    A = pi * r^2 + pi * r * s

    s = sqrt(r^2 + h^2)

    s/r = 5/3

    3s = 5r

    3 * sqrt(r^2 + h^2) = 5r

    9 * (r^2 + h^2) = 25r^2

    9r^2 + 9h^2 = 25r^2

    9h^2 = 16r^2

    3h = 4r

    h = (4/3) * r

    V = (1/3) * pi * r^2 * h

    96 * pi = (1/3) * pi * r^2 * (4/3) * r

    96 = (4/9) * r^3

    96 * (9/4) = r^3

    24 * 9 = r^3

    216 = r^3

    6 = r

    h = (4/3) * r

    h = (4/3) * 6

    h = 8

    Lateral area is the area of the cone minus the base

    A = pi * r * s

    A = pi * r * sqrt(r^2 + h^2)

    A = pi * 6 * sqrt(6^2 + 8^2)

    A = pi * 6 * sqrt(100)

    A = pi * 6 * 10

    A = 60pi

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