4.4 triangles
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Transcript 4.4 triangles
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QUIZ!
Where is the base of a parallelogram?
#2
Where is the height of a parallelogram?
#3
What is the formula for finding the area of a
parallelogram?
#4
Find the area of this parallelogram.
7 cm
4 cm
#5
Find the area.
9 cm
2 cm
#6
Find the area.
10.25 cm
3.5 cm
#7
Find the circumference.
2.6 mm
#8
Find the diameter.
Circumference = 82 mm.
#9
Find the radius.
Circumference = 9.7 ft
#10
What is the area of the gardens only? The gardens are
the green triangles.
2 ft
4 ft
2 ft.
9 ft
1
Any side is the base of the parallelogram.
2
A perpendicular line connecting parallel lines.
Or
A line that is drawn through the parallelogram.
3
A=bxh
4
A=bxh
A=7x4
A = 28 cm
5
A=bxh
A=9x2
A = 18 cm
6
A=bxh
A = 10.25 x 3.5
A = 35.875
7
C = 2Лr
C = 2 x 3.14 x 2.6
C = 16.25 mm
8
C = Лd
82 = 3.14 x d
82 ÷ 3.14 =
D = 26.11 mm
9
9.7 = 2Лr
9.7 = 2 x 3.14 x r
9.7 ÷ 6.28 = r
r = 1.54 ft
10
Area of Parallelogram:
A = 9 x 4 = 36 ft
Area of Rectangle:
A = 11 x 4 = 44 ft
Area of Rectangle – Area of Parallelogram:
44 – 36 = 8 ft.
The gardens are 8 ft total. One garden is 4 ft.
Lesson 4.4
Formula
The formula for finding the area of a triangle is:
A = bh ÷ 2
When you draw a diagonal in a parallelogram, it makes 2
congruent triangles.
Congruent means that the triangles are EXACTLY the
same, but they are not in the same orientation.
The area of the two congruent triangles is equal to the area
of the parallelogram.
So, the area of one triangle is ½ the area of a parallelogram.
To find the area of a triangle in a parallelogram, divide
the area of the parallelogram by 2.
Area of parallelogram ÷ 2 = Area of Triangle
What is the area of each triangle?
6 cm
8 cm
Find the area of the parallelogram. Then find the area
of the triangles.
9 cm
5 cm
Example;
A = bh ÷ 2
A=6x4÷2
4 cm
A = 12 cm
6 cm
Area of Parallelogram = 8 x 6 = 48 cm
Area of one triangle = 48 ÷ 2
Therefore one triangle = 24 cm
A = bh ÷ 2
9 cm
A=9x9÷2
A = 40.5 cm
9 cm
Find the area:
4 cm
Draw the triangles and find the area.
B=3
H = 4.5
B=7
H = 10.7
B = 1.6
H = 2.9
B = 8.4
H = 8.4
Homework...
Answer the questions on the board.
Workbook 4.4
Textbook page 146 #5, 9, 10, 11