Perimeter Power Slides
Perimeter Power
Mastering the Boundaries of Our World
What is Perimeter?
The perimeter is the total distance around the outside of a shape.
Think of it like a fence around a yard or a frame around a picture.
AROUND
"Peri" (Around) + "Metron" (Measure)
The Secret Formula
Step 1: Identify
Look at all the side lengths of the shape.
5 cm
3 cm
5 cm
3 cm
Step 2: Add
Add all the side lengths together!
5 + 3 + 5 + 3 = 16
The perimeter is 16 cm
Regular Rectangles
The Rectangle Rule
Opposite sides are equal! If you know two sides, you know them all.
10 in ? 4 in ?
10 + 4 + 10 + 4 = 28 inches
5 ft
Speedy Squares
All sides are the same!
5 + 5 + 5 + 5 = 20 ft
Or: 4 x 5 = 20 ft
Wild Shapes
Not every shape is a rectangle! Some are irregular.
The Golden Rule remains:
- Count every single side.
- Don't skip any numbers!
- Add them up carefully.
8 cm 4 cm 4 cm 4 cm 4 cm 8 cm
Practice Challenge
Can you solve this perimeter puzzle?
12 m 12 m 10 m
Calculate the Perimeter:
12 + 12 + 10 = ?
!
Don't forget the units: meters!
You are now a
Perimeter Pro
Ready for Independent Patrol!
Pick up a pencil
Open your worksheet
Start patrolling!
Perimeter Patrol Worksheet
Perimeter Patrol
Field Report: 3rd Grade
Agent:
Date:
Mission: Calculate the total distance around each shape. Show your addition.
Sector 1: Standard Structures
1
A rectangular park fence.
12 ft 8 ft
Work Space:
Perimeter: ft
2
A square garden patch.
9 m 9 m
Work Space:
Perimeter: m
Sector 2: Irregular Shapes
3
Triangle warning sign.
15 in 15 in 10 in
Work Space:
Perimeter: in
4
L-shaped deck layout.
7 m 4 m 3 m 3 m 4 m 7 m
Work Space:
Perimeter: m
Sector 3: Cold Case Files
5
Find the missing side!
The total perimeter is 24 cm.
8 cm ? 4 cm 4 cm
Work Space:
Missing side: cm
6
Detective Challenge
Detective Sam walks around a rectangular block once. The long side is 100 meters. The short side is 50 meters. Total meters walked?
Calculation:
Total Distance: meters
Final Checklist
Added all sides?
Included units?
Checked math?
Perimeter Patrol Answer Key
Perimeter Patrol
Official Answer Key
Mission Control: Use this key to verify patrol reports. Verify both calculation and units.
Sector 1: Standard Structures
1
A rectangular park fence.
12 ft 8 ft
Calculation:
12 + 8 + 12 + 8 = 40
Perimeter: 40 ft
2
A square garden patch.
9 m 9 m
Calculation:
9 + 9 + 9 + 9 = 36
Perimeter: 36 m
Sector 2: Irregular Shapes
3
Triangle warning sign.
15 in 15 in 10 in
Calculation:
15 + 15 + 10 = 40
Perimeter: 40 in
4
L-shaped deck layout.
7 m 4 m 3 m 3 m 4 m 7 m
Calculation:
7+4+3+3+4+7 = 28
Perimeter: 28 m
Sector 3: Cold Case Files
5
Find the missing side!
8 cm ? 4 cm 4 cm
Calculation:
8+4+4 = 16
24 - 16 = 8
Missing side: 8 cm
6
Detective Challenge
100 + 50 + 100 + 50 = 300
Total Distance: 300 meters