Concept of Perimeter

The perimeter is the total distance around the outside edge or boundary of any closed two-dimensional shape (a plane figure). If you were to walk along every side of a park and return to your starting point, the total distance you walked would be the perimeter.

Why is it Important? Understanding perimeter is fundamental in many real-world tasks, such as:

• Planning how much fencing is needed for a garden or yard.

• Calculating the length of decorative border or trim required for a room.

• Measuring the length of a running track or sports field boundary.

Perimeter = Sum of all side lengths

• Centimeter (cm) – For small objects

• Meter (m) – For medium to large objects

• Kilometer (km) – For very large areas

• 1 cm = 1/10 dm, and 1 m = 100 cm

Important: When calculating perimeter, ensure all measurements are in the same unit before adding them together.

Find the perimeter

Solution:

Required perimeter

= AB + BC + CD + DE + EF + FG + GA

= 6.2 cm + 4 cm + 8 cm + 4 cm + 8 cm + 4 cm + 6.2 cm

= 40.4 cm 

The lengths of adjacent sides of rectangle ABCD are 4 cm and 5 cm.

Since opposite sides of a rectangle are equal:

Perimeter = 2 × (Length + Breadth)

= 2 × (5 + 4)

= 18 cm

• Perimeter = sum of all side lengths of a closed figure

• Always convert measurements to the same unit before calculating

• Unit of perimeter is always linear (cm, m, km, etc.)

• Method: Identify all side lengths → Convert to same unit → Add all values → Write answer with unit