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SAI International School

Sub – Mathematics

Class - IV

Topic – Geometry

Sub-topic 6 : - Circle and its parts

 Introduction – If we put a bangle or a coin on the plane of the paper and move our pencil
around it, we obtain a closed figure shown below:

Such a closed figure is called a circle.

Basically, a circle a simple closed figure all of whose points are at the same distance from a
fixed point inside it.

Real life Examples: cap of the bottle, bangles, carom dots etc...

Parts of the circle:

a. Centre: The fixed point inside the circle is called the centre.
b. Circumference: The length of the boundary of the circle is known as circumference.
c. Radius: The distance between the centre and any point on the circumference of circle is
called its radius.
d. Radii: The plural of radius is known as radii.
e. Chord: A line segment which joins any two points on the circumference of the circle is
known as chord.
f. Diameter: The chord that passes through the centre is known as diameter.

Naming the parts of the circle:

a. Point O is the centre.