Perimeter
PERIMETER
Ms. Cuervo
CAHSEE Prep
Your family has moved to California from New York and you’re are excited to swim in the public pool. You know how to swim, but your sister does not. You must figure out the best way to make sure your sister does not get too close to the water.
What is the easiest way to keep your sister from going into the pool?
Introduction
Building a fence around the pool is one way to keep your sister safe.
12 feet
18 feet 18 feet
12 feet
In order to determine how much fencing is needed, answer the following:
• What shape is created by the fencing around the pool?
Rectangle
• How many sides does this shape have?
4
• What is the length of each side?
18 ft, 18 ft, 12 ft, 12 ft
• How much fencing is needed to surround the pool?
60 feet (add up the sides!)
Perimeter
7MG 2.1 Students will find the perimeter of polygons.
VOCABULARY
Perimeter – The distance around a polygon (found by adding the lengths of the sides)
*Perimeter only includes the outside of a figure, so you do not need to consider the inside part of the object.
How do you find the perimeter of a shape? Click here to watch VIDEO!
What’s Perimeter?
When you find the distance around the edges of an object, you find the perimeter. Perimeter only includes the outside of a figure, so you do not need to consider the inside part of the object.
16 inches
Perimeter =
16 in + 12 in + 16 in + 12 in =
56 in
16 inches
18 feet
12 feet
18 feet
Perimeter = side + side + side + side
= 18 ft + 12 ft + 18 ft + 12 ft
= 60 feet
12 feet
Finding the Missing Side
5 cm 5 cm
6 cm 6 cm
7 cm
The perimeter of this polygon is 29 cm . What is the length of the missing side?
What strategy can you use to find the missing side length?
Work backwards!
29cm – 22cm = 7 cm
8 in
3 in
3 in
2 in
Putting It All Together
4 in
?
Ramon is trying to find the perimeter of this figure, but must find the length of the missing side before he can determine the perimeter. All sides meet at 90 degree angles.
What information already given in the figure will help Ramon find the length of the missing side?
The lengths of the other sides.
What do you know about opposite sides of this shape?
They are equal .
2 in
4 in
Missing side: 8in - 4in = 4 in
Perimeter: 8in + 3in + 3in + 2in + 2in + 4in + 4in +4in = 30 in
Exit Slip
Find the Perimeter of Talawn’s Future
Rectangular Pool.
6 ¼
yards
12 ¾
