1. Areas of Parallelograms, Triangles, Trapezoids and Rhombi

2. Area of a Parallelogram
If a parallelogram has an area of A square units, a base of b units, and a height of h units, then
A = bh

3. Examples Let’s use the parallelogram from our previous example. 5 4
What is the height of this
parallelogram? 11
It is 4 units. The height is always the
perpendicular distance from one side to the
opposite side.
What is the base of this parallelogram?
It is 11 units. The base is the one of the two sides from
which the height is measured.
So, A = bh
A = (11 units) (4 units) =
44 units 2

4. Work this problem 12 in. Find the area of the parallelogram A = bh
A = (12 in.) (20 in.)
A = 240 in. 2

5. Area of a Triangle
If a triangle has a base of b units, and a height of h units, then A = ½ bh.
A = ½ bh
A = ½ (23 ft.)(6 ft.)
A = 69 ft. 2
6 ft.
Height
Base
23 ft.

6. Work this problem 7 ft. 11 ft. A = ½ bh A = ½ (11 ft.)(7 ft.)
A = 38.5 square feet

7. Area of a Trapezoid
A trapezoid has bases of b1 and b2 units, and a height of h units, then
A = ½ h (b1 + b2)
8 in.
base 2 or b2
height
A = ½ h (b1 + b2)
7 in.
A = ½ (7 in.) (15 in. + 8 in.)
A = ½ (7 in.) (23 in.)
base 1 or b1
A = ½ (161 in. 2 )
15 in.
A = 80.5 in. 2

8. Area of a Rhombus A = ½ d1 d2, where d1 and d2 are diagonals.
AC = 12 in. A B
A = ½ d1 d2
A = ½ (12 in.)(21 in.)
BD = 21 in. D C
A = ½ (252 in.2) = 126 in.2