1. Areas of Parallelograms, Triangles and Rectangles
Objective - Students will use variables in expressions describing geometric quantities such in parallelograms by using a formula and scoring an 80% proficiency on an exit slip.

2. Formula for Area of Rectangle
Area = Length X Width
6cm w
A= l w
10cm
A=10cm x 6cm l
A=60cm 2

3. Parallelograms
A parallelogram is a quadrilateral where the opposite sides are congruent and parallel.
A rectangle is a type of parallelogram, but we often see parallelograms that are not rectangles (parallelograms without right angles).

4. Area of a Parallelogram
Any side of a parallelogram can be considered a base. The height of a parallelogram is the perpendicular distance between opposite bases.
The area formula is A=bh
A=bh
A=5(3)
A=15m2

5. Area of a Parallelogram
If a parallelogram has an area of A square units, a base of b units, and a height of h units, then
A = bh.
Example 2
Base = 15 cm
Height = 12 cm
Area = 15 cm x 12 cm
Area = 180 sq. cm

6. Ex. 3 Find the missing unit
A= base x Height
A = bh
Area= 56 cm squared
Base= _______
Height= 8 cm

7. Area of Rectangles and Triangles
Objective: Students will use variables in expressions describing geometric quantities for Areas by using formulas and scoring an 80% proficiency on an exit slip.

8. Area of a Triangle A triangle is a three sided polygon.
Any side can be the base of the triangle.
The height of the triangle is the perpendicular length from a vertex to the opposite base.
A triangle (which can be formed by splitting a parallelogram in half) has a similar area formula: A = ½ bh.

9. Example1
A= ½ bh
A= ½ (30)(10)
A= ½ (300)
A= 150 km2

10. Example 2
14.6 cm
A= ½ bh
18.7 cm
A= ½
A= ½ A=

11. Triangle Vocabulary
Copy this down on your graphic organizer!

12. Vocabulary Review Right Angle - 90˚ or perpendicular
Obtuse Angle – any triangle with one angle > 90˚
Acute Angle – any triangle with one angle < 90˚
Equilateral Triangle – all sides of the triangle are the same length
Isosceles Triangle – 2 sides of the triangle are same length
Scalene Triangle – No sides of the triangle are the same length
Congruent – The same thing
Congruent shapes can be the same but in a different orientation (direction)

13. Formulas to Know! A = l w A = s² A = b h A = ½ b h or b h 2
Add these to your graphic organizer!

14. Complex Figures Step 1: Find what shapes make up the complex figure
Step 2: Make a grocery list of what you know
Step 3: Use the appropriate formula to find the area of each shape that makes up the whole.
Step 4: Add the areas together for the total area.
If there is another part to the question, use your critical thinking skills to determine how to get the answer

15. Example Step 1: Split the shape into a rectangle and triangle.
24 cm
10 cm
| 27 cm |
Step 1: Split the shape into a rectangle and triangle.
Step 2: The rectangle is 24cm long and 10 cm wide.
The triangle has a base of 3 cm and a height of 10 cm.
l= 24cm w= 10cm b=(27cm – 24cm) 3cm h=10cm

16. Step 3 & 4 Rectangle Triangle A = ½ bh A = lw A = ½ (3)(10) A = 24(10)
A = 240 cm2
A = ½ (30)
A = 15 cm2
Total Figure
A = A1 + A2
A = = 255 cm2

17. Draw and Do this in your notebook!
20 cm
5 cm
| 26 cm |

18. Solution Rectangle Triangle A = ½ bh A = lw Total Figure A = A1 + A2

19. work Time Textbook Questions Page 145-147 #2, 5, 9, 11
Homework: Lesson 4.4
Page 87-89
(In H/W and Practice Book)