Results 1 to 3 of 3
Like Tree1Thanks
  • 1 Post By princeps

Math Help - Shadows and distance, I need a formula to solve for Object 2

  1. #1
    Newbie
    Joined
    Feb 2012
    Posts
    4

    Shadows and distance, I need a formula to solve for Object 2

    Looking for a formula to solve this word problem. Please Help

    A shadow from object 1 projects on a wall 1.75 X larger than its original size. Object 1 is 4.5 ft from the wall the shadow has been casted on. Object 2 has a known size which cast a shadow of 1.25 X its original size. How far is object 2 from the wall.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member
    Joined
    Nov 2011
    From
    Crna Gora
    Posts
    420
    Thanks
    64

    Re: Shadows and distance, I need a formula to solve for Object 2

    Quote Originally Posted by crah28 View Post
    Looking for a formula to solve this word problem. Please Help

    A shadow from object 1 projects on a wall 1.75 X larger than its original size. Object 1 is 4.5 ft from the wall the shadow has been casted on. Object 2 has a known size which cast a shadow of 1.25 X its original size. How far is object 2 from the wall.
    Let :

    r_1=1.75~ , r_2=1.25~ ,x_1=4.5 ~ , x_2 = ?

    and denote distance of the source of the light from the wall as d . Therefore :

    d=r_1(d-x_1) \Rightarrow d=1.75(d-4.5) \Rightarrow d=10.5

    Hence :

    d=r_2(d-x_2) \Rightarrow x_2=\frac{dr_2-d}{r_2} \Rightarrow x_2=2.1
    Thanks from crah28
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Feb 2012
    Posts
    4

    Thumbs up Re: Shadows and distance, I need a formula to solve for Object 2

    Thanks for your help, the formula was spot on.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 0
    Last Post: February 29th 2012, 08:28 AM
  2. Distance of Falling Object
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: February 3rd 2010, 11:22 AM
  3. Replies: 1
    Last Post: October 6th 2009, 01:12 PM
  4. Replies: 4
    Last Post: June 30th 2009, 06:18 AM
  5. Shadows
    Posted in the Calculus Forum
    Replies: 1
    Last Post: December 2nd 2006, 11:28 PM

Search Tags


/mathhelpforum @mathhelpforum