1. Summary

Closed figure:A figure with no open ends is a closed figure.

Regular closed figures: A closed figure in which all the sides and angles equal.

Perimeter:

Perimeter is the distance covered along the boundary forming a closed figure when we go round the figure once. The concept of perimeter is widely used in real life.

Eg: 1) For fencing land. 

2) For building a compound wall around a house.

The perimeter of a regular closed figure is equal to the sum of its sides.

Perimeter of a rectangle:

Perimeter of a square:

Equilateral triangle:

A triangle with all its sides and angles equal is called an equilateral triangle.

The perimeter of an  equilateral triangle with the side 'a'

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