1. Finding area of circle using circumference

2. Relationship between diameter and radius:
Diameter of a circle is twice of its radius.
Formula:
Diameter = 2 x radius
Radius = r O r A B d

3. Pi (π)
The ratio of circumference to diameter is constant for all circles. This ratio is called Pi and is written as π. Where π = C = π ⇒
C = πd ⇒
C = 2πr d 22 7

4. Area of a circle Area of the circle = πr² sq. units
The area of a circle is given by the formula
Area of the circle = πr² sq. units

5. Given:- Circumference = 88m To Find:- Area of circle
Example 1: The circumference of a circle is 88 m. Find the area of the circle.
Solution
Given:- Circumference = 88m To Find:- Area of circle
We know that Area = πr²
Since radius(r) is not given we find radius(r) using Circumference
We know that Circumference = 2πr 2
Divide 88 and 44 by 44
r = 2 x 7= 14 cm

6. Now we have found radius, Lets us now calculate area of circle
We know that Area of circle = πr² 2
Divide 14 and 7 by 7
Area = 22 x 2 x 14 = 616 cm2 (Ans)

7. Given:- Circumference = 132m To Find:- Area of circle
Example 1: The circumference of a circle is 132 m. Find the area of the circle.
Solution
Given:- Circumference = 132m To Find:- Area of circle
We know that Area = πr²
Since radius(r) is not given we find radius(r) using Circumference
We know that Circumference = 2πr 12
Divide 121 and 44 by 11 4
r = 84/4 = 21 cm

8. Now we have found radius, Lets us now calculate area of circle
We know that Area of circle = πr² 3
Divide 21 and 7 by 7
Area = 22 x 3 x 21 = 1386 cm2 (Ans)

9. Try these
The circumference of a circle is 44 m. Find the area of the circle.