Theory:

Yashini visited a theme park with her family on summer vacation. There she saw a gigantic Roller coaster, Merry-Go-Round, Ferris wheel. Before she left, she had eaten pizza, and pancake then played with the frisbee.
 
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She wondered if there was something familiar to the things she encountered at the theme park. Then she realized that all the things she had seen are circled in shape.
 
We also had seen/used many objects in our daily life that are circled shape objects.
Example:
1. The tire of vehicles which is the prominent invention by the ancient people.
2. A clock
3. A ring
4. The foods we eat such as pizza, and dosa
5. CD drive, bangles and coins etc,.
Now we get a clear overview about circles, then let us get to know more about circles.
 
Circle:
A closed line consisting of all points on the plane that are equidistant from a given point on the plane is called a circle.
Diameter of the circle:
  • The distance across the circle.
  • The length of any chord (a straight line which connects two points on a circle) passing through the center.
  • It is twice the radius.
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Diameter \(=\) \(2 ×\) Radius \(=\) \(2r\)
  
Radius of the circle:
The radius is the distance from the center to any point on the circle.
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Radius is also known as half of the diameter.
 
Radius=Diameter2
  
Important!
The value of the π [pi] can be either \(22/7\) or \(3.14\).