Number of Square Units

What is the number of square units enclosed by the polygon ABCDE?
Source: NCTM Mathematics Teacher 2006

SOLUTION

Polygon HEJC encloses polygon ABCDE.
Number of square units inside polygon HEJC
9\times 10=90
Number of square units inside polygon GBC
6\div 2=3
Number of square units inside polygon HIBG
4
Number of square units inside polygon IAB
(4\times 4)\div 2=8
Number of square units inside polygon EJD
(5\times 10)\div 2=25
Number of square units inside polygon ABCDE
90-3-4-8-25=50

Answer: 50 square units

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About mvtrinh

Retired high school math teacher.
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