10.4 Area of Triangles and Trapezoids
At the end of this section:
1) I can use the formula for the area of a triangle and I can describe why differently shaped triangles can have the same area
2) I can use the formula for the area of a trapezoid
Area of a Triangle = 1 bh
2
h = height of the triangle
b = base
The height is marked with a dashed line that is perpendicular to a side of the triangle
the base of the triangle is the side that is perpendicular to the height
Examples) Identify the height and the base of the triangle, then find the area.
12
12
10
6
4
5
6
9
Title: Mar 6­9:19 PM (1 of 7)
Pop the balloon next to each triangle that has it's base and height labeled correctly.
4
3
6
5
9
4
10
7
3
7
1
1.5
Title: Mar 6­10:17 PM (2 of 7)
Your Turn:
Find the area of each triangle. a)
5
3
4
7
b)
13
5
12
c)
9
8
15
Title: Mar 6­9:56 PM (3 of 7)
5
Find the base and height of each triangle
Find the area of each triangle
How is it possible for these 3 triangles to have same area even though they are different types of triangles?
Title: Mar 6­10:39 PM (4 of 7)
2) Trapezoids
1
Area of a Trapezoid = h(b1 + b2) 2
6
A = 4
10
Your Turn:
Find the area of each trapezoid.
3
a)
7
9
11
b)
4
5
7
3
Title: Mar 6­10:34 PM (5 of 7)
Copy the trapezoid exactly. Label the parts.
b2
h
Cut out the 2 trapezoids
b1
Arrange the 2 trapezoids so that the diagonal sides meet
This forms a ________________. What is the length and width of the new figure?
Using the formula to find the area of the figure formed by the 2 trapezoids, how could we figure out the area formula for a trapezoid?
Title: Mar 6­10:55 PM (6 of 7)
Title: Apr 6­7:51 AM (7 of 7)