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SAI International School
CLASS-VII

Mathematics
CHAPTER- 11: Area and Perimeter
LESSON NOTES- 4

SUBTOPIC: Area of Circle

Introduction:A circle is a simple closed shape where all points have the same
distance from the centre.
 We have seen many shapes such as wheel, dining plate, coin etc. All these
shapes are in the form of circle.
 The center of a circle is the center point in a circle, from which all the
distances to the points on the circle are equal.
 The radius is the distance from the center to any point on the circle.
 Diameter of the circle is defined as the distance across the circle.
 The length of any chord passing through the center is called the diameter of
the circle. It is twice the radius. i.e. diameter = 2 x radius (d = 2r)


In the given figure O is the centre, OP is the
radius and PQ is the diameter of the circle.

Area of the Circle:Let r be the radius of circle.

 Now, area of circle = π x (radius) = π x r = πr 2
2
2

22
 The value of π (pi) is approximately or 3.14.
7

 Hence the area of a semicircle will be half of the area of the circle.

To find the Area of the Circle: Let us find the area of a circle, using paper.
 Draw a circle and shade one half of the circle.