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Understanding Perimeter and Area
Geometry
Mr. Zampetti
Unit 5, Day 1
Objective
• To be able to find the area and perimeter of squares and rectangles
Work Together
•Get into groups of 3.
•Everyone needs ½ piece of graph paper.
•Each person in the group should complete one of the following:
•A rectangle with length 5 units and width 3 units
•A rectangle with length 8 units and width 2 units
•A rectangle with each side 4 units.
Work Together
1. Record the perimeter of each rectangle
2. Are the rectangles with equal perimeters congruent, similar, or neither?
3. Record the area of each rectangle.
4. Are the rectangles with the same area congruent, similar, or neither?
5. Do the rectangles with equal perimeters have the same area?
Definition
• Perimeter – the sum of the lengths of the sides
b
b
hh
Perimeter of a Rectangle
• P = 2b + 2h OR P = 2(b+h)
Find the Perimeter
10
4
Perimeter = 28
Perimeter of a Square
• P = 4s
s
s
s
s
Find the Perimeter
• If one side of a square is 6, what is the perimeter?
• 24
Definition
• Area – the number of square units enclosed by the polygon
Postulate 5-1
• The area of a square is the square of the length of a side.
• A = s2
• If the side of a square is 5, what is the area?
• 25
Try This:
• What is the area of a square whose sides are 12 in. long?
• What is the area of a square whose sides are 1 ft long?
• How many square inches are in a square foot?
Postulate 5-2
• If two figures are congruent, their areas are equal
Theorem 5-1: Area of a Rectangle
• The area of a rectangle is the product of its base and height
• A = bh
• To find the area, you must use the same units for all dimensions!!!
b
b
hh
Real World Examples
• You are designing a rectangular banner that will be 2 yd long and 4 ft wide. How much material would you need?
• You are making a sign with the length 75cm and width 2m. What is the area?
Find the Perimeter and Area to the following:
10 in
6 in3in
3in
Perimeter = 32in Area = 51in2
Homework
Work Packet:
Understanding Perimeter and Area
