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Math Help - unknown answer?

  1. #1
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    Question unknown answer?

    hi i also have this other equation which i am unsure of, just wondering if you can help which is:

    A square steel plate is pierced by a square tool leaving a margin of 20mm all round. The area of the hole is one third of that of the original plate. calculate the dimensions of the original plate.

    thanks again!
    jenko!
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  2. #2
    Super Member

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    Lexington, MA (USA)
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    Hello, jenko!

    Did you make a sketch?


    A square steel plate is pierced by a square tool leaving a margin of 20mm all round.
    The area of the hole is one-third of that of the original plate.
    Calculate the dimensions of the original plate.
    Code:
          :  20 :   x-40    :  20 :
       -  * - - - - - - - - - - - * -
      20  |                       | :
       -  |     * - - - - - *     | :
       :  |     |           |     | :
       :  |     |           |     | :
     x-40 |     | x-40      |     | x
       :  |     |           |     | :
       :  |     |    x-40   |     | :
       -  |     * - - - - - *     | :
      20  |                       | :
       -  * - - - - - - - - - - - * -
          : - - - - - x - - - - - :

    The side of the original plate is: . x mm.
    . . Its area is: . x^2 mm.

    The side of the hole is: . x - 40 mm.
    . . Its area is: . (x-40)^2 m.


    The area of the hole is one-third the area of the plate.
    . . There is our equation! . . . . . (x-40)^2 \:=\:\frac{1}{3}x^2

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