Perimeter
Key Notes :
The perimeter of a shape is the distance around the outside of the shape. Find the perimeter by adding the lengths of the sides.
- Definition: Perimeter is the total length of the boundary of a two-dimensional shape.
- Importance: It helps us measure and understand the outer boundaries of various figures.
I. Basic Concepts of Perimeter:
A. Calculation: Sum of all the sides of a shape.
B. Units: Perimeter is measured in the same units as the length of the sides (e.g., centimeters, meters, etc.).
II. Perimeter of Common Shapes:
A. Rectangles and Squares: 1. Formula: P = 2(l + w) for rectangles, P = 4s for squares. 2. Explanation: Add up the lengths of all four sides.
B. Triangles: 1. Formula: P = a + b + c (sum of all three sides). 2. Explanation: Combine the lengths of the three sides.
C. Circles: 1. Formula: P = 2πr or πd (circumference). 2. Explanation: Involves the concept of radius (r) or diameter (d).
Learn with an example
What is the Perimeter ?
________Kilometers
Look at the shape and find the length of each side. Add the lengths:
12+12+12=36
Now find the units. The lengths are measured in kilometres, so the perimeter is also measured in kilometres.
The perimeter is 36 kilometres.
What is the Perimeter of this rectangle ?
_________centimeters
In a rectangle, opposite sides have the same length. Look at the rectangle and find the side lengths. add:
5+4+5+4=18
Now find the units. The lengths are measured in centimetres, so the perimeter is also measured in centimetres.
The perimeter is 18 centimetres.
What is the Perimeter ?
_________centimeters
Look at the shape and find the length of each side. Add the lengths:
20+16+12=48
Now find the units. The lengths are measured in centimetres, so the perimeter is also measured in centimetres.
The perimeter is 48 centimetres.
let’s practice!
