1. Review: Area of
2-D Shapes
Keystone Geometry

2. Squares and Rectangles
Area of Rectangle: A = bh
Area of Square: A = s² s
A = s² h b
A = bh
Example:
Example: 12 5 6
A = 6² = 36 sq. units
A = 12 x 5 = 60 sq. units

3. Area of Circles Area of Circle: A =  r² A = (9)² = 81  sq. cm r
Example:
A = (9)² = 81  sq. cm

4. Triangles and Trapezoids
h is the distance from a vertex of the triangle perpendicular to the opposite side.
h is the distance from b1 to b2, perpendicular to each base h b b1 b2

5. Ex: Triangles and Trapezoids7 6 8 12

6. Parallelograms & Rhombi
Area of Parallelogram: A = bh h b 8 10
Example: 6 9
Example:
A = 9 x 6 = 54 sq. units
A = ½ (8)(10) = 40 sq units

7. Area of Regions
The area of a region is the sum of all of its non-overlapping parts. 8 10 12 4 14
A = ½(8)(10)
A= 40
A = (12)(10)
A= 120
A = (4)(8)
A=32
A = (14)(8)
A=112
Area = = 304 sq. units

8. Areas of Regular Polygons
If a regular polygon has an area of A square units, a perimeter of P units, and an apothem of a units, then
A = ½ (a)(p). 8
Perimeter = (6)(8) = 48
apothem =
Area = ½ (48)( ) = sq. units