Download Finding the area of a Trapezoid

Finding the area of a
Trapezoid
SWBAT find the area of a trapezoid by decomposing it
into two triangles and using the formula.
Do Now
1.
Marianna makes a 5% commission on the appliances she sells. If she earns $600 in
salary but needs to earn a total of $975 for her paycheck, how much merchandise will
she have to sell?
2. Three angles, A, B, and C, are supplementary. Angles A and C are
congruent. Angle C is 54 degrees. What is the measure of angle B?
3. Find the perimeter of a triangle whose legs each measure 4x+2
and the base is 2(x + 3).
Vocabulary
-Trapezoid: a 4-sided flat shape with straight sides that has a
pair of opposite sides parallel.
- Decomposing: breaking a shape up into two other shapes (Ex:
a trapezoid into 2 triangles)
Review:
What does parallel mean?
How do we measure height?
Area of a Trapezoid
Draw a diagonal line to break the trapezoid into two
Find the area of each triangle
Add the area of each triangle together
See the diagram below.
triangles.
10 in
5 in
12 in
Example.
12 cm
Find the area of the figure by
drawing a diagonal and splitting it
into two triangles.
12 cm
10 cm
11 cm
9 cm
click to reveal
11 cm
9 cm
10 cm
The Area (A) of a trapezoid is also found by using the formula:
Note: The base & height always form a right angle!
10 in
5 in
12 in
Try These.
Find the area of the figures using
the formula.
12 ft
8 ft
8 ft
7 ft
9 ft
click to reveal
10
7
6
8
13
click to reveal
Exit Ticket:
Explain in words two methods to find the area of a
trapezoid. Include visuals.
Who did
Ms.
Dalton
meet this
weekend
?