1. Area of circle using geometric shapes

2. Recap- Circumference of circle - Application
We know that perimeter is measuring the outside of any shape.
Let us learn how to calculate perimeter by small Illustration of using rope length.
Let us take a rope of x length and try reshaping the rope into a square as given below.
X length
From this, its clearly seen that Perimeter of a square = length of the rope.
In case of circle perimeter is circumference
Circumference of circle = length of rope

3. Example 1:
A wire in the shape of a rectangle of length 37 cm and breadth 29 cm is reshaped in the form of a circle.
Find the radius and area of the circle.
 Solution
Given: rectangle’s length (l)= 37 cm , breadth(b) = 29 cm
To Find : Radius and area of the reshaped shape - circle  
Step1:- To find perimeter of rectangle
We know that perimeter of rectangle = 2 (l + b)
= 2 x ( )
= 2 x 66 =132 cm
Step2:- To find radius of circle
perimeter of rectangle = circumference of a circle 3
Divide 132 and 44 by 11 12
Divide 12 and 4 by 4 4
r = 3 x 7 = 21 cm (Ans1)

4. Step3:- To find area of circle
We know that Area = πr² 3
Divide 21 and 7 by 7
Area = 22 x 3 x 21 = 1386cm2 (Ans2)

5. To Find : Radius and area of the reshaped shape circle
Example 2:
A silver wire when bent in the form of a square encloses an area of 121 sq cm. if the same wire is bent in the form of circle. Find the area of circle.
Solution Given: area of square = 121 cm2 To Find: area of resized shape - circle
To Find : Radius and area of the reshaped shape circle
Since circle is resized shape , Perimeter of square = perimeter of circle
To find area of circle, we first need to
Step 1: Find side of square ,using area of square
Step 2 : Find perimeter of square, using side of square
Step 3: Find radius of circle , using perimeter of circle which is same as perimeter of square
Step 4: Find area of circle, using radius of circle
Step 1: Find side of square ,using area of square
We know that area of square = a x a
121 = a x a
121 = 11 x 11
a =11 cm

6. Step 2 : Find perimeter of square, using side of square
We know that perimeter of square = 4 x a
= 4 x 11 = 44 cm
Step 3: Find radius of circle , using perimeter of circle which is same as perimeter of square
We know that perimeter of circle =2 π r
Divide 44 and 44 by 44
r = 7cm
Step 4: Find area of circle, using radius of circle
We know that Area of circle = πr²
Area = 22 x 7= 154 cm2 (Ans)

7. Try these
A wire in the shape of a rectangle of length 25 cm and breadth 19cm is reshaped in the
form of a circle.
A copper wire when bent in the form of a square encloses an area of 81 sq. cm.If the
same wire is bent in the form of a circle. Find the area of the circle.