Area of a blue polygon
Geometry
Level
pending
Find the area of the shaded polygon in the unit grid shown above.
The answer is 20.5.
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1 solution
The area of the blue polygon is equal to the area of the red rectangle minus the sum of the areas of five small triangles and one square. So the area is
6
(
5
)
−
2
1
[
2
(
1
)
+
1
(
4
)
+
1
(
3
)
+
1
(
5
)
+
1
(
3
)
]
−
1
(
1
)
=
2
0
.
5