11.1 and 11.2

Area Formulas

and Parallelogra

ms

Rectangle

Area of a rectangle = bh• b = base

• h = height

Square

• Area of a square = s2, • s = side

Example 1:

5

15

10

5

25

8

8

8

10

10

14

14

20

20

(–5, 4) (2, 4)

(2, –3) (–5, –3)

(0,0)

Find the area of the following figures.

Example 2: a. Find the area of a square whose side is 9

b. Find the area of a square whose diagonal is 18

c. Find the side of a square whose area is 64

d. Find the perimeter of a square whose area is 100

e. Find the area of a square whose perimeter is 64

Example 3:

20 12

28

40

Find the area of the shaded region. (Assume right angles)

11.2 Parallelograms

Area of a Parallelogram

Theorem 100

The area of a parallelogram is equal to the product of the base and the height.

A = bh

where b is the length of the base and h is the height.

Area of a Triangle

Theorem 101

The area of a triangle is equal to one-half the product of a base and the height (or altitude) for that base.

A∆ = 1/2bh

where b is the base of the triangle and h is the altitude.

Example 1:

6

13

5

12 5

8

Find the total area of each figure. (In each figure the triangle is mounted on a rectangle.)

Example 2:

• Find the base of a parallelogram of height 18 and area of 252.

Example 3:Find the area of the obtuse triangle.

24

60º

5

Now you try!

Solve for x.