Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Polygon problem (? )

  1. Jan 19, 2010 #1
    polygon problem (?!!)

    Hi there!:smile:
    I have got an problem here.It's a simple one.Not much to think about
    "The ratio between the numbers of sides of two regular polygons is 1:2 and the ratio between the sum of their 3:4.Find the number of sides in each polygon"
    It appears easy and is too. but the problem is the answer i am getting is absolutely wierd ie.,
    -1 and -2 sides .:uhh:
    In the work out I had considered the no . of sides to be x and 2x
    the sum of interior angles 3y and 4y respectively.
    so it ends up as {(4x-4)*90} -{(2x-4)*90} =4y-3y
    =>180x=y
    so i sustituted it in the equation (2x-4)*90=3y which ends up as -4=4x .: x= -1:eek::uhh::
    Book's answers are polygon with 5 and 10 sides .
    I don't know whether I have gone wrong some where:confused:. If so Please help me correct it!(If the book's answer is wrong mention that too :smile:!)
    Thank you
     
  2. jcsd
  3. Jan 19, 2010 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi 1/2"! :smile:
    If you mean "the ratio between the sum of their interior angles is 3:4", then I agree, the solution is -1 and -2 ! :biggrin:

    A solution of 5 and 10 would have a ratio of 3:8, not 3:4.
     
  4. Jan 23, 2010 #3
    Re: polygon problem (?!!)

    Thanks tiny-tim.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook