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Perimeter
Perimeter is the distance covered along the boundary forming a closed figure when you go round the figure once.
Perimeter Of rectangle
Perimeter Of rectangle is given by the Formula
$P=2 (L + B)$
Where L and B are the length and Breadth
Perimeter Of Regular Shapes
Area
The amount of surface enclosed by a closed figure is called its area.
It is measured in number of square of 1 m or 1cm in the enclosed area
How To estimate Area
We estimate the area using the below rules
Place the figure on a squared paper or graph paper where every square measures 1 cm × 1 cm.
Now find out the number of squares using below rules
The area of one full square is taken as 1 sq unit. If it is a centimetre square sheet, then area of one full square will be 1 sq cm.
Ignore portions of the area that are less than half a square.
If more than half of a square is in a region, just count it as one square.
If exactly half the square is counted, take its area as 1/2 sq cm
Area of Rectangle
Area Of rectangle is given by the Formula
$A=L\times B$
Where L and B are the length and Breadth
Area of Square
Area Of Square is given by the Formula
$A=4 \times L$
Where L is the side of the square
Examples
Example 1: Rectangle Perimeter
A rectangle has a length of 10 cm and a breadth of 6 cm. Find its perimeter. Solution:
\(P = 2(l+b)\)
\(P = 2(10 + 6)\)
\(P = 2(16)\)
\(P = 32\) cm
Example 2: Square Area
A square has a side length of 4 cm. Find its area. Solution:
\(A = s^2\)
\(A = 4^2\)
\(A = 16\) sq cm
Example 3: Equilateral Triangle Perimeter
A Equilateral triangle has sides of length 7 cm. Find its perimeter. Solution:
\(P = a+b+c\)
\(P = 7 + 7 + 7\)
\(P = 21\) cm
Example 4: Pentagon Perimeter
A Pentagon triangle has sides of length 11 cm. Find its perimeter. Solution:
\(P = 5 \times L\)
\(P = 55\)cm
Area of Composite shapes
While calculating the area of composite figures, you can break down the shape into simpler shapes, calculate their individual areas, and then add/subtract them as needed.
Always remember to include units in your answers for clarity.
Example
By splitting the following figures into rectangles, find the area (The measures are given in centimetres) Solution:
We can split that in 1 square of 1 cm and 1 rectangle of 3 x 4
So Area= 1 + 12= 12 sq cm
