Bellwork

Find the area of the triangle below.

11.3 Area of Trapezoids

Students will be able to find the area of trapezoids given information regarding the height, bases and/or median.

Discover

With your partner, follow the directions on the sheet you’ve been given. One/partner.

Trapezoid

b1

b2

h1 2( )

2

h b bA

>

>

Area of a Trapezoid

Theorem: The area A of a trapezoid whose bases have lengths b1 and b2 and whose altitude has length h is given by

1 2

1( )

2A h b b

Median (Defn)

The median of a trapezoid is the segment that connects the ____________ of the legs of the trapezoid.

The median can be found by finding the _____________ of the bases.

1 2

2

b bmedian

1 2

1

2median b b

Trapezoid Area formula (2)

1 2

1( )

2bA h b

( )me nA h dia

1 2

1( )2

A h b b

Chapter 11 Toolbox

Fill in all the formulas we’ve talked about so far in Chapter 11.

You will be expected to know these and will not be given a formula sheet.

Group work

In your groups, complete the 5 problems.I will randomly select 5 people from each

group to draw and present each problem. Be sure you are ready!

When finished, start your homework!

Example 1

Find the area of the isosceles trapezoid.

Example 2

Find the area of a trapezoid if its height is 5 inches and the median of the trapezoid is 12 inches.

Example 3

Find the area of the trapezoid below.

Example 4

Find the shorter base of a trapezoid if the area is 52 square meters, its altitude is 8 meters and its longer base is 10 meters.

Example 5

The consecutive sides of an isosceles trapezoid are in the ratio 2:5:10:5, and the trapezoid’s perimeter is 44. Find the area of the trapezoid.

Homework

Pg. 525 # 2, 3 ,4, 7b, 8a, 9, 10, 12

Extra Credit #17

Quiz over 11.1-11.4 Wednesday

Example 6

Find the area of this figure.   

A. 24 B. 92  C. 99 D. 68

11.4

33

4

4

5

20

14

5