Quadrilaterals: by this smart lady in Arizona
Geometry
Level
2
Find the area of the quadrilateral shown in the figure.
Note: Figure not drawn to scale
144
127.5
183
171
149
151
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1 solution
"ABD is a right triangle; hence BD2 = 152 + 152 = 450
Also BC2 + CD2 = 212 + 32 = 450
The above means that triangle BCD is also a right triangle and the total area of the quadrilateral is the sum of the areas of the two right triangles.
Area of quadrilateral = (1/2)×15×15 + (1/2)×21×3 = 144"
(Dr Abdelkader Dendane, https://www.analyzemath.com/high school math/grade_10/geometry.html)