Closed figure:A figure with no open ends is a closed figure.
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'
Area
The amount of surface enclosed by a closed figure is called its area.
The following conventions are to be adopted while calculating the area of a closed figure using a squared or graph paper.
 Count the fullyfilled squares covered by the closed figure as one square unit or unit square each.
 Count the halffilled squares as half a square unit.
 Count the squares that are more than halffilledas one square unit.
 Ignore the squares filled less than half.
For example, the area of this shape can be calculated as shown:
Covered area

Number

Area estimate (sq. units)

Fully filled squares

6

6

Half–filled squares

7

7 x ½

Squares filled more than half

0

0

Squares filled less than half

0

0

Area covered by full squares = 6 x 1 = 6 sq. units
Area covered by half squares = 7 x ½ = 7/2= 3 ½ sq. units
Total area of the given shape = 6 + 3 ½ sq. units
Thus, the total area of the given shape = 9 ½ sq. Units
Area of a rectangle can be obtained by multiplying length by breadth. Area of the square can be obtained by multiplying side by side.
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