Circles

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It is a round, closed shape.

The circumference of a Circle

The circumference of a circle refers to the distance around the circle.

  • Radius: A straight line from the Circumference till the centre of the circle.
  • Diameter: It refers to the line from one point of the Circumference to the other point of the Circumference.
  • π (pi): It refers to the ratio of a circle’s circumference to its diameter.

Circumference(c) = π × diameter

C = πd

= π × 2r

 diameter (d) = twice the radius (r)

 d = 2r

Example

What is the circumference of a circle of diameter 12 cm (Take π = 3.14)?

Solution

C = πd

C = 3.14 × 12

= 37.68 cm

Area of Circle

Area of the circle = πr2

Example

Find the area of a circle of radius 23 cm (use π = 3.14).

Solution

R = 23 cm

π = 3.14

Area of circle = 3.14 × 232

= 1,661 cm2

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