Question 1002922
You forgot about the fact that the triangles have base = height = 9 (since 9 is 1/3 of 27)


Also, the area of the square is not 4*9 it is 9*9


Finally, you don't add in the square cutout. You subtract it off.


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Area of paper = s*s = 27*27 = 729
Area of triangles = 4*(b*h)/2 = 4*(9*9)/2 = 162
Area of square cutout = 9*9 = 81


Area of sketch = (Area of paper) - (triangles) - (square cutout)
Area of sketch = (729) - (162) - (81)
Area of sketch = 486 square inches