Results 1 to 3 of 3

Math Help - Don't get surface area questions

  1. #1
    Newbie
    Joined
    Oct 2012
    From
    New York
    Posts
    5

    Don't get surface area questions

    I posted this last night but I have since gotten answers for one of the questions but still do not get two at all.

    1. "Find the total surface area of the following figure.
    Hint: The surface area formula for the cone includes the base of the cone. Substract this value."
    Image:
    http://www.omegamath.com/scripts/geometry/Gtest/image924.gif

    I do not get this at all. Someone please just respond with clear directions on how I measure the surface area for this particular image. An answer would be appreciated too of course, it would help in figuring out how I do this!

    2. "Find the total surface area of the following figure. The back of the figure is a rectangle. Disregard the bottom of the figure."
    Image:
    http://www.omegamath.com/scripts/geometry/Gtest/image925.gif

    This one seems to be the same way, so same deal as #1.

    Thank you in advance!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor MarkFL's Avatar
    Joined
    Dec 2011
    From
    St. Augustine, FL.
    Posts
    1,988
    Thanks
    734

    Re: Don't get surface area questions

    1.) The lateral surface area of a cone is:

    A_1=\pi rl

    where r is the radius and l is the lateral height.

    The surface area of a hemisphere is:

    A_2=\frac{2}{3}\pi r^3

    Now add these the get the total area:

    A=A_1+A_2=\pi rl+\frac{2}{3}\pi r^3=\frac{\pi r}{3}\left(3l+2r^2 \right)

    Now use r=2\text{ cm} and l=5\text{ cm} to find the surface area of the given solid.

    2.) The back of the figure is a rectangle having a base b of 16 in and a height h of 7 in.

    The area of a rectangle is A_R=bh

    The two sides are trapezoids having big base B of 7 in and little base b of 3 in and height h of 3 in.

    The area of a trapezoid is A_T=\frac{h}{2}(B+b)

    The front is two rectangles. The vertical rectangle has a base of 16 in and a height of 3 in, and the slanted rectangle has a base of 16 in and a height which is the hypotenuse of a right triangle having legs of 3 in and 4 in. Using the Pythagorean theorem, we find this is:

    \sqrt{3^2+4^2}=5

    So, put this all together to find the requested surface area.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Dec 2012
    From
    ny
    Posts
    1

    Re: Don't get surface area questions

    I am always fond of mathematics and find it really interesting. Some parts of it like trigonometry always troubled me with the formulas. Even integral calculus was really hard to understand. You are maintaining a nice math forum here.for details
    _________________________________
    Gasper Millan
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Calculate the surface area of the surface
    Posted in the Calculus Forum
    Replies: 2
    Last Post: June 26th 2009, 04:03 AM
  2. Lateral Area and Total Surface Area
    Posted in the Geometry Forum
    Replies: 1
    Last Post: May 25th 2009, 04:28 PM
  3. Two questions involving surface area.
    Posted in the Calculus Forum
    Replies: 15
    Last Post: January 23rd 2009, 04:56 AM
  4. Help finding surface area of a surface
    Posted in the Calculus Forum
    Replies: 1
    Last Post: October 3rd 2008, 04:11 PM
  5. Volume, Surface Area, and Lateral Surface Area
    Posted in the Geometry Forum
    Replies: 1
    Last Post: April 14th 2008, 11:40 PM

Search Tags


/mathhelpforum @mathhelpforum