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Math Help - Help with three geometry problems!

  1. #1
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    Help with three geometry problems!

    Got these questions on a practice quiz and am a bit confused with them. I can do any other of these but these three leave me confused. Assistence is appreciated!

    1. Find the total surface area of the following figure. (it gives a hint saying "The surface area formula for the cone includes the base of the cone. Substract this value."

    2. Find the total surface area of the following figure. The back of the figure is a rectangle. Disregard the bottom of the figure.

    3. The total surface area of a sphere is 100 pie in 2. Find the radius.

    Thank you in advance!
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  2. #2
    Senior Member MaxJasper's Avatar
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    Re: Help with three geometry problems!

    1) assuming that the top surface is a complete hemisphere we have:

    cone area = pi*(r=2)*5 = 10*pi

    hemisphere are= 2*pi*r^2
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  3. #3
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    Re: Help with three geometry problems!

    Quote Originally Posted by MaxJasper View Post
    1) assuming that the top surface is a complete hemisphere we have:

    cone area = pi*(r=2)*5 = 10*pi

    hemisphere are= 2*pi*r^2
    So does that mean the surface area is 10pi cm? As in that would be the answer I'm putting in? Or do I have to combine the hemisphere AND cone area?
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  4. #4
    Senior Member MaxJasper's Avatar
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    Re: Help with three geometry problems!

    combine
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  5. #5
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    Re: Help with three geometry problems!

    So I have the hemisphere at 12 and the cone at 14.7 after calculating the surface area of both then dividing each number by pi separately Adding the post-division numbers together gets me 26.7-pi centimeters squared. Did I do this right?
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