area of quadrilaterals and triangles. what is a quadrilateral? any polygon with four sides and four...
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Area of Quadrilaterals and Triangles
What is a quadrilateral?
•Any polygon with four sides and four vertices (or corners)
•All sides must be straight
Area of square, rectangle, and parallelogram•Area is a measure of the amount of space
contained inside a closed figure•The area of a square, rectangle, or
parallelogram is the product of its base and height:▫Area = base height
Find the area:
•A = b h•A = 11 5•A = 55 cm2
•A = b h•A = 6 4•A = 24 in2
• Which measurement is the base?
11cm• Which measurement
is the height? 5cm
The TRAPEZOID•The trapezoid is a quadrilateral with one
pair of parallel sides that are opposites▫The parallel sides are the “bases”▫The non-parallel sides are the “legs”▫The height is the distance between the
bases
Area of a Trapezoid•Since the bases are not the
same length, we have to take the average of them to find the area▫Average of bases = ½ (b1 + b2)
•Next, multiply the average of the bases by the height to get the area
Area of Trapezoid = ½ h(b1 + b2)
Find the area:
•Find the average of the bases▫½ (b1 + b2)▫½ (9 + 5)▫ = 7
•Multiply by the height▫6 7 = 42 in2
Triangles
•A triangle is half of a rectangle or half of a parallelogram
•If we know the area of a rectangle or parallelogram is base height, what could the are of a triangle be? Remember, a triangle is halfArea = ½
bh
Find the area
•Area = ½ bh•Area = ½ (108)•Area = ½80•Area = 40 mm2
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