Answer:
392.5 in²
Explanation:
The area of a composite figure is found by decomposing it into areas that you have formulas for. This figure is easily decomposed to a trapezoid and a rectangle.
Trapezoid
The base lengths of the trapezoid are 20 in and 9 in. Its height is the difference between the height of its top base (21 in) and the height of its bottom base (16 in). That difference is 5 in.
A = 1/2(b1 +b2)h
A = 1/2(20 in + 9 in)(5 in) = 72 1/2 in²
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Rectangle
The area of a rectangle is the product of its base and height.
A = bh
A = (20 in)(16 in) = 320 in²
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Total area
The area of the whole figure is the sum of the areas of its parts.
area = trapezoid area + rectangle area
area = 72 1/2 in² +320 in² = 392 1/2 in²