Review: Area of 2-D Shapes Keystone Geometry

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

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

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

Ex: Triangles and Trapezoids 7 6 8 12

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

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 = 40 + 120 + 32 + 112 = 304 sq. units

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