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Math Help - Volume and SA of a cylinder.

  1. #1
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    Volume and SA of a cylinder.

    i have a cylinder here i need to find the volume and the surface area

    the cylinder is 4cm base height 15cm

    would the volume be 3.14 x 42 x 15 = 753.6 i have to give the answer to 3 significant figures so 754cm.

    and would the surface area be

    2 x 3.14 x 4 x 15 + 2 x 3.14 x 42 = 194.68 i have to give the answer to 2 siginificant figures so 190cm!

    is that right?????
    Last edited by mr fantastic; May 11th 2010 at 07:19 PM. Reason: Re-titled.
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  2. #2
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    Quote Originally Posted by thierryvoomhenry View Post
    i have a cylinder here i need to find the volume and the surface area

    the cylinder is 4cm base height 15cm

    would the volume be 3.14 x 42 x 15 = 753.6 i have to give the answer to 3 significant figures so 754cm.

    and would the surface area be

    2 x 3.14 x 4 x 15 + 2 x 3.14 x 42 = 194.68 i have to give the answer to 2 siginificant figures so 190cm!

    is that right?????
    Dear thierryvoomhenry,

    The volume is correct. But you should better check the surface area. It should be, 477.28

    Hope this will help you.
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  3. #3
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    Hmmm, I am pretty sure the formulas are as following:



    Therefore, the correct volume is 188.496 or 188 (3 sig figures) and the correct surface area is 213.628 or 214 (3 sig figures)

    I think both of your are taking the radius as 4 cm whereas that's the length of the base, which can be used as a diamter but half that is the radius of that cylinder.

    Hope this helps!
    Last edited by unstopabl3; May 11th 2010 at 12:36 PM.
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  4. #4
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    Dear unstopabl3,

    Yes you are correct. When he says "the cylinder is 4cm base" it is most probably the diameter.
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