14.1 Areas of Polygons and Circles

Area on a Geoboard (or dot paper)

→ addition method: sum the area of the figure by finding the area of the smaller parts and then adding them together

Figure

a) b)

→ subtraction method: Figure

Examples

Figure a) and b)

Area of a Rectangle

Figure

Formula: A = lw

Example: Find the area of each rectangle (Figure a) and b))

Area of a Parallelogram

Formula: A = bh

Area of a Triangle

Formula: A = ½ bh

Examples: Find the area for each (Figure)

a) A = bh

b) A = bh

c) A = ½ bh

d) A = ½ bh

e) A = ½ bh

Area of a Trapezoid

Figure

Formula: A = ½ h (b1 + b2)

Examples: Figure

a) b)

Area of a Regular Polygon

Figure

Formula: A = ½ ap

Area of a Circle

Figure

Formula: A =