Perimeter

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Perimeter
What does it mean?
Let’s find the perimeter.
12 ft
8 ft
10 ft
Let’s find the perimeter.
15 in
20 in
20 in
10 in
Let’s find the perimeter.
This is a regular polygon.
What is a regular polygon?
So, if one of this
polygon’s sides
measures 5 cm...
A regular polygon is one in
which all sides are the same
length.
…what would the
perimeter of this
polygon be?
Let’s find the perimeter.
5 cm
5 cm
5 cm
5 cm
5 cm
5 cm
5 cm
5 cm
5 cm
5 cm
So, how would you find the
perimeter of this rectangle?
length
???
So, how would you find the
perimeter of this rectangle?
length
???
width
length
So, how would you find the
perimeter of this rectangle?
length
width
width
length
So, how would you find the
perimeter of this rectangle?
length
length + length + width + width =
width
2 x length + 2 x width =
2l + 2w =
length
width
So, how would you find the
perimeter of this rectangle?
7 mm
???
So, how would you find the
perimeter of this rectangle?
7 mm
???
5 mm
7 mm
So, how would you find the
perimeter of this rectangle?
7 mm
2l + 2w =
2x7+2x5=
5 mm
14 + 10 =
7 mm
5 mm
Find the Perimeter
10 ft
2l + 2w =
8 ft
2 x 10 + 2 x 8 = 0
20 + 16 =
10 ft
8 ft
Find the Perimeter
3 in
2l + 2w =
2x7+2x3=
14 + 6 =
7 in
???
???
Rectangle Perimeter Formula
2 in
2l + 2w = perimeter of a rectangle
2 x length + 2 x width
2l + 2w =
6 in
2x6+2x2=
12 + 2 x 2 =
12 + 4 =
Find the Perimeter
Use: 2l + 2w = perimeter of a rectangle
10 yds
1 yds
Step 1: Write the formula.
Step 2: Replace the variables.
Step 3: Multiply first.
Step 4: Add last.
Step 5: Write the answer
with the correct units.
2l + 2w =
2 x 10 + 2 x 1 =
20 + 2 =
20 + 2 = 22
22 yds
Find the Perimeter
Use: 2l + 2w = perimeter of a rectangle
9 in
3 in
Step 1: Write the formula.
Step 2: Replace the variables.
Step 3: Multiply first.
Step 4: Add last.
Step 5: Write the answer
with the correct units.
2l + 2w =
2x9+2x3=
18 + 6 =
18 + 6 = 24
24 in
Try one with someone at your table.
Use: 2l + 2w = perimeter of a rectangle
4 cm
8 cm
Step 1: Write the formula.
Step 2: Replace the variables.
Step 3: Multiply first.
Step 4: Add last.
Step 5: Write the answer
with the correct units.
2l + 2w =
2x8+2x4=
16 + 8 =
16 + 8 = 24
24 cm
So, how would you find the
perimeter of this square?
side
side
side
side
So, how would you find the
perimeter of this square?
side
side + side + side + side =
4 x side =
side
side
side
4s =
So, how would you find the
perimeter of this square?
7 mm
4s =
4x7=
7 mm
7 mm
7 mm
So, how would you find the
perimeter of this square?
4s =
5 ft
5 ft
4x5=
5 ft
5 ft
Square Perimeter Formula
4s = perimeter of a square
3 in
4 x side
4s =
4x3=
Find the Perimeter
Use: 4s = perimeter of a square
10 yds
Step 1: Write the formula.
Step 2: Replace the variables.
Step 3: Multiply and write the
correct units in your answer.
4s =
4 x 10 =
4 x 10 = 40 yds
Find the Perimeter
Use: 4s = perimeter of a square
9 cm
Step 1: Write the formula.
Step 2: Replace the variables.
Step 3: Multiply and write the
correct units in your answer.
4s =
4x9=
4x9=
36 cm
Try one with someone at your table.
Use: 4s = perimeter of a square
6 mm
Step 1: Write the formula.
Step 2: Replace the variables.
Step 3: Multiply and write the
correct units in your answer.
4s =
4x6=
4x6=
24 mm
Let’s Review
What does perimeter mean?
•Perimeter is the distance around the edge of an
object.
What is the formula for finding the
perimeter of a rectangle?
What is the formula for finding the
perimeter of a square?
Now it is your turn.

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