Lauretta J. Fox
Altitudes drawn from each endpoint of the upper base separate a trapezoid into three non overlapping polygons-two triangles and a rectangle. The area of the trapezoid is equal to the sum of the areas of these three polygons. A formula to find the area of a trapezoid may be derived as follows:
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Area of a Trapezoid = 1/2 x Altitude x Sum of the Bases
Example:
Find the area of a trapezoid whose bases are 10 cm. and 14 cm. and whose altitude is 6 cm. Iong.
Solution:
A = 1/2h(b1+ b2) A= 1/2 x 6(10 + 14)= 3 x 24= 72 sq. cm.
Suggested Assignment:
Using polygons, design a house or other building. Find the areas of the exterior walls, the roof, the doors, and the windows.
Exercises:
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Find the areas of the following figures:
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9. At $8.50 a square yard, what is the cost of laying a cement floor in a garage that is 6 yards long and 7 yards wide?
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10. At $1.85 a square yard, find the cost of painting the front and rear gables of a house 18 ft. wide, the height of the ridge above the eaves being 10 ft.
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11. QRST is a rectangle. Find the area of:
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