Transcript Points, Lines, and Planes

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
Perimeter of a Rectangle
• P = 2b + 2h
OR P = 2(b+h)
b
h
h
b
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
b
• A = bh
h
h
b
• To find the area, you must use the same units
for all dimensions!!!
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 in
3in
3in
Perimeter = 32in
Area = 51in2
Homework
Work Packet:
Understanding
Perimeter and Area