Results 1 to 5 of 5

Math Help - radius given a point on circumference

  1. #1
    Newbie
    Joined
    Sep 2010
    Posts
    3

    radius given a point on circumference

    I have a word problem:
    A pipe is against a wall. There is a point on the circumference that is both ten inches from the wall and five inches from the ground. Give two possibilities for the radius of the pipe.

    I guess that it has something to do with substituting (10,5) in the standard formula for a circle, but that leaves me with three variables.

    Any help would be appreciated greatly.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,129
    Thanks
    1010
    Quote Originally Posted by hokusai View Post
    I have a word problem:
    A pipe is against a wall. There is a point on the circumference that is both ten inches from the wall and five inches from the ground. Give two possibilities for the radius of the pipe.

    I guess that it has something to do with substituting (10,5) in the standard formula for a circle, but that leaves me with three variables.

    Any help would be appreciated greatly.
    Is the pipe running horizontally? ... vertically? ... some other direction???

    seems to me the 2" from the ground is not necesssary to solve this unless there is some other info you haven't provided.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Sep 2010
    Posts
    3

    re: skeeter

    there is a diagram included, i have attempted to reproduce it:
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,129
    Thanks
    1010
    the pipe is tangent to a right angled corner ...

    the center of the circle is at the point (r,r)

    so, the circle's equation is (x-r)^2 + (y-r)^2 = r^2

    sub in the given values, x = 10 and y = 5 , and solve for r ... you will get two solutions.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Sep 2010
    Posts
    3
    wow that seems so much simpler than having the center at say (h,k) and trying to solve (10-h)^2 + (5-k)^2 = r^2
    funny how the simplest and most obvious can be so elusive
    much thanks
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 12
    Last Post: November 22nd 2009, 05:02 PM
  2. Replies: 3
    Last Post: September 5th 2009, 07:13 PM
  3. Replies: 1
    Last Post: April 20th 2009, 04:26 AM
  4. Replies: 2
    Last Post: April 11th 2008, 03:03 AM
  5. [SOLVED] [SOLVED] Radius, Area And Circumference- Help!
    Posted in the Geometry Forum
    Replies: 2
    Last Post: January 14th 2008, 04:12 PM

Search Tags


/mathhelpforum @mathhelpforum