Hello, ncooks!
Welcome aboard!
Find the area of the shaded region. Code:
9
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13 *::::::::::* | 2
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The area of the rectangle is: .$\displaystyle 9 \times 13 \:=\:117\text{ cm}^2$
Assuming that the diagonal lines are parallel,
. . the white regions are two congeuent parallelograms,
. . each with base 2 and height 9.
The white region has area: .$\displaystyle 2 \times (2\times 9) \:=\:36\text{ cm}^2$
Therefore, the area of the shaded region is: .$\displaystyle 117 - 36 \:=\:81\text{ cm}^2$
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An easier way . . .
Remove the white strips and push the shaded regions together. Code:
9
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9 |:::*:::::::::::*
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