Results 1 to 14 of 14

Math Help - Pythagoras' Theorem in geometry question.

  1. #1
    Newbie
    Joined
    Nov 2011
    Posts
    13

    Pythagoras' Theorem in geometry question.

    Sophie built a small tower, made of bricks, in her back garden. On top of it she fitted a large glass light-bulb holder.

    The diagram shows it as part of a circle.

    Centre, C, is 20 centimetres above the top of the wall.

    1. Calculate the radius of the circular bulb holder.

    2. Use this to find the total height of the structure.


    Here's the diagram :
    Attached Thumbnails Attached Thumbnails Pythagoras' Theorem in geometry question.-emewl.png  
    Last edited by mr fantastic; November 18th 2011 at 08:18 PM. Reason: Re-titled.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    radius of the circle is 20 cm (you really need to have a look at the definition of a radius)

    total height = height of the wall + diameter of the circle
    Follow Math Help Forum on Facebook and Google+

  3. #3
    -1
    e^(i*pi)'s Avatar
    Joined
    Feb 2009
    From
    West Midlands, England
    Posts
    3,053
    Thanks
    1

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    Quote Originally Posted by Kyleee View Post
    Sophie built a small tower, made of bricks, in her back garden. On top of it she fitted a large glass light-bulb holder.

    The diagram shows it as part of a circle.

    Centre, C, is 20 centimetres above the top of the wall.

    1. Calculate the radius of the circular bulb holder.

    2. Use this to find the total height of the structure.


    Here's the diagram :
    Unless I'm missing something obvious isn't the radius 20cm?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Nov 2011
    Posts
    13

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    Just to let you guys know : I know what the radius is (half the diameter of a circle), but my teacher said it's an exam question and I'm in the highest maths class. How the heck can it be that easy?
    Last edited by mr fantastic; November 18th 2011 at 08:01 PM.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Nov 2011
    Posts
    13

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    Quote Originally Posted by skeeter View Post
    radius of the circle is 20 cm (you really need to have a look at the definition of a radius)

    total height = height of the wall + diameter of the circle
    I also thought of this too, but I didn't really think this was correct. I think I've did something like this before and I did it like the way you've just said it and I got it wrong. D:
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Newbie
    Joined
    Nov 2011
    Posts
    13

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    Sorry guys, the diagram is wrong, i'll upload the correct one in a minute.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Nov 2011
    Posts
    13

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    There! New diagram up; now can you help me?
    Follow Math Help Forum on Facebook and Google+

  8. #8
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    Quote Originally Posted by Kyleee View Post
    There! New diagram up; now can you help me?
    one word for you ... Pythagoras.
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Newbie
    Joined
    Nov 2011
    Posts
    13

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    Skeeter, I know it's pythagoras (that's what my teacher said), but where are the triangles? Please help, I really need to do this. D:
    Follow Math Help Forum on Facebook and Google+

  10. #10
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    r^2 = 22^2 + 15^2
    Attached Thumbnails Attached Thumbnails Pythagoras' Theorem in geometry question.-geometry1.jpg  
    Follow Math Help Forum on Facebook and Google+

  11. #11
    Newbie
    Joined
    Nov 2011
    Posts
    13

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    Quote Originally Posted by skeeter View Post
    r^2 = 22^2 + 15^2
    Okay, I know this now, thanks.
    But now I need to do question 2 : find the height of the whole thing.

    Would I just double the answer and add it to 55? Orrrr...

    Edit : Okay, that's totally wrong what I just said. I got muddled up. :P

    Would I just do 20 + 55 + ? =
    Follow Math Help Forum on Facebook and Google+

  12. #12
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    Quote Originally Posted by Kyleee View Post
    Okay, I know this now, thanks.
    But now I need to do question 2 : find the height of the whole thing.

    Would I just double the answer and add it to 55? Orrrr...

    Edit : Okay, that's totally wrong what I just said. I got muddled up. :P

    Would I just do 20 + 55 + ? =
    where did 20 come from?
    Follow Math Help Forum on Facebook and Google+

  13. #13
    MHF Contributor
    Joined
    Dec 2007
    From
    Ottawa, Canada
    Posts
    3,080
    Thanks
    66

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    Well, it's obvious to me that the line shown as 22 is really 20;
    that makes radius = sqrt(15^2 + 20^2) = 25.
    So height = 55 + 20 + 25 = 100.
    All in favor raise your hands !!
    Follow Math Help Forum on Facebook and Google+

  14. #14
    MHF Contributor

    Joined
    Mar 2011
    From
    Tejas
    Posts
    3,279
    Thanks
    670

    Re: Please help with this maths question, it's quite easy, I just don't know it. :D

    the diagram and the wording of the problem are inconsistent. this should be resolved.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Pythagoras' Theorem.
    Posted in the Geometry Forum
    Replies: 2
    Last Post: February 19th 2011, 03:08 AM
  2. Trigonometry,Pythagoras and Circle Theorem Question
    Posted in the Trigonometry Forum
    Replies: 2
    Last Post: May 3rd 2010, 04:59 PM
  3. Geometry (Pythagoras)
    Posted in the Geometry Forum
    Replies: 5
    Last Post: March 12th 2007, 12:11 PM
  4. Pythagoras' theorem
    Posted in the Geometry Forum
    Replies: 6
    Last Post: February 20th 2007, 11:00 AM
  5. pythagoras theorem
    Posted in the Geometry Forum
    Replies: 3
    Last Post: August 1st 2005, 06:17 PM

Search Tags


/mathhelpforum @mathhelpforum