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Math Help - Areas and Perimeters?

  1. #1
    Newbie suckatmaths's Avatar
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    I did these problems, teacher said they were wrong and sent me away to do them again. I tried and still got the same answers.
    *

    A) Find the perimeter to the figure
    B) The Enclosed area:

    Picture:

    12002.jpg picture by EdenJonas - Photobucket

    Thanks
    Last edited by mr fantastic; May 31st 2009 at 04:59 AM. Reason: Merged posts and attendant editing
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  2. #2
    Moo
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    Hello,
    Quote Originally Posted by suckatmaths View Post
    I did these problems, teacher said they were wrong and sent me away to do them again. I tried and still got the same answers.
    *

    A) Find the perimeter to the figure
    B) The Enclosed area:

    Picture:

    12002.jpg picture by EdenJonas - Photobucket

    Thanks.
    Please provide the results (and the working) you got. It would be easier to see where the mistakes are, if there are any. What do you find ? I have the answers...
    Last edited by mr fantastic; May 31st 2009 at 05:01 AM. Reason: Merged posts and attendant editing
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  3. #3
    Newbie suckatmaths's Avatar
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    A) 10squared + 8squared=
    100+64
    =164
    =squareroot164 = 12.80

    10+8+12.80 = 30.8cm.

    (see? I suck)

    B) 1/2 12.80x8

    6.4x8
    =51.2

    I did really bad.
    There is just this major question mark next to them.
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  4. #4
    Moo
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    Quote Originally Posted by suckatmaths View Post
    A) 10squared + 8squared=
    100+64
    =164
    =squareroot164 = 12.80

    10+8+12.80 = 30.8cm.

    (see? I suck)

    B) 1/2 12.80x8

    6.4x8
    =51.2

    I did really bad.
    There is just this major question mark next to them.
    Okay, your mistake comes from the application of the Pythagorean theorem.


    In a right angle triangle, the hypotenuse is the longest side. It is also the side opposit to the right angle. So here, the hypotenuse is the side which length is 10.
    And the Pythagorean theorem says (\text{Hypotenuse})^2=(\text{Side}_1)^2+(\text{Sid  e}_2)^2

    Hence the length of the third side is not 10^2+8^2, but... ?
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  5. #5
    Newbie suckatmaths's Avatar
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    6squared? :\
    I'm sorry, I am really bad at this.

    Oh wait, is it = 10squared = 8squared + 6squared?
    Last edited by suckatmaths; May 31st 2009 at 01:45 AM. Reason: mistake.
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  6. #6
    Moo
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    Quote Originally Posted by suckatmaths View Post
    6squared? :\
    I'm sorry, I am really bad at this.

    Oh wait, is it = 10squared = 8squared + 6squared?
    Yes

    So the length of the third side is 6 ! (not 6squared... read carefully the formula from the Pythagorean theorem)
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  7. #7
    Newbie suckatmaths's Avatar
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    So therefore do I just:

    10squared + 8squared + 6squared = perimeter?

    Then squareroot = perimeter?
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  8. #8
    Moo
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    Quote Originally Posted by suckatmaths View Post
    So therefore do I just:

    10squared + 8squared + 6squared = perimeter?

    Then squareroot = perimeter?
    Okay... It looks like you have big problems with basics


    The perimeter is the sum of the sides that are on the outside.
    This means that the perimeter of your figure is 8+10+the length of the semicircle.
    You're not asked for the perimeter of the triangle !!!

    Now, do you know the formula for the perimeter and the area of a circle ?
    What is the radius of this semicircle ?


    The perimeter of the triangle would be 8+10+6.
    Not with the squares. Please read carefully the formula from the Pythagorean theorem !
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  9. #9
    Newbie suckatmaths's Avatar
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    Radius of the semicircle is 3.

    Do I go: 3*pi = 9.42m

    Then add: 9.42 + 10 + 8

    The perimeter = 27.42m?
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  10. #10
    Moo
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    Quote Originally Posted by suckatmaths View Post
    Radius of the semicircle is 3.

    Do I go: 3*pi = 9.42m

    Then add: 9.42 + 10 + 8

    The perimeter = 27.42m?
    Exactly !

    But did you understand the path to come up with this solution ?
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  11. #11
    Newbie suckatmaths's Avatar
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    Yay, it only took me forever. Ahahaha.
    Thank you for all your help on that one.

    Quote Originally Posted by Moo View Post
    Exactly !

    But did you understand the path to come up with this solution ?
    Yes, I finally got there. I have to READ the question, and work out everything... The perimeter of not JUST the triangle, but the circle aswell.
    So thank you.
    Last edited by mr fantastic; May 31st 2009 at 05:02 AM. Reason: Merged posts
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