Results 1 to 6 of 6

Math Help - Scale Factor

  1. #1
    Newbie
    Joined
    Jul 2010
    Posts
    12

    Scale Factor

    I'm having trouble with scale factor, particularly these two problems.

    The areas of the bases of two similar square pyramids have the ratio 25:9. What is the ratio of their volumes?

    The volumes of two similar rectangular prisms are in a ratio of 81:3000. Find the surface area of the larger solid if the smaller is 126m^2.

    Please help or try and explain.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,492
    Thanks
    1393

    Re: Scale Factor

    Quote Originally Posted by Destroyer0203 View Post
    I'm having trouble with scale factor, particularly these two problems.

    The areas of the bases of two similar square pyramids have the ratio 25:9. What is the ratio of their volumes?

    The volumes of two similar rectangular prisms are in a ratio of 81:3000. Find the surface area of the larger solid if the smaller is 126m^2.

    Please help or try and explain.
    If you scale a shape's side length by some factor (k), then its area is scaled by the square of that scale factor (k^2) and its volume is scaled by the cube of the scale factor (k^3). In the first, you know something about how the areas are scaled. Can you work out how the side lengths are scaled? From there can you work out how the volumes are scaled?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jul 2010
    Posts
    12

    Re: Scale Factor

    so if you have the area you could do the square root so you get 5:3 then since its volume you cube it and get 125:27?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,492
    Thanks
    1393

    Re: Scale Factor

    Yes
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Jul 2010
    Posts
    12

    Re: Scale Factor

    ok, so i get the first one, how would you approach the 2nd one?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,492
    Thanks
    1393

    Re: Scale Factor

    Quote Originally Posted by Destroyer0203 View Post
    ok, so i get the first one, how would you approach the 2nd one?
    All the information you need is in my previous post.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 0
    Last Post: July 19th 2011, 11:45 AM
  2. scale factor
    Posted in the Algebra Forum
    Replies: 8
    Last Post: April 20th 2009, 01:56 AM
  3. Scale factor
    Posted in the Algebra Forum
    Replies: 3
    Last Post: January 27th 2009, 02:08 AM
  4. Scale factor
    Posted in the Algebra Forum
    Replies: 4
    Last Post: January 10th 2009, 08:06 PM
  5. Scale Factor???
    Posted in the Algebra Forum
    Replies: 1
    Last Post: May 19th 2008, 04:15 AM

Search Tags


/mathhelpforum @mathhelpforum