Transcript 4.4 triangles

Yes, you have it...Another POP
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