Answer:
$129
Explanation:
The cost is given in terms of dollars per square foot. In order to determine the cost of the window, you need to figure out how many square feet of glass Mrs. Humphrey will be buying.
The window is shaped like a trapezoid. The formula for the area of a trapezoid is ...
A = 1/2(b1 +b2)h
where b1 and b2 are the parallel base lengths, and h is the perpendicular height between those bases.
Here, we have b1 = 6 ft, b2 = 2 ft, h = 1.5 ft. Putting these numbers into the formula gives ...
A = 1/2(6 ft +2 ft)(1.5 ft) = 1/2(8 ft)(1.5 ft) = (1/2)(8)(1.5) ft² = 6 ft²
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So, Mrs. Humphrey is buying 6 square feet of glass at a cost of $21.50 per square foot. Her cost will be ...
(6 ft²)($21.50/ft²) = $(6×21.50) = $129.00
The replacement window will cost $129.00.