# RD Sharma Solutions for Class 7 Maths Chapter 21:Mensuration – 2 (Area of Circle)

The RD Sharma Class 7 Maths Chapter 21 mensuration 2 deals with the definition of the circle where students obtain in-depth knowledge about the properties of circles. A circle is nothing but a round-shaped figure that contains no corners or edges. In other words, in geometry, a circle can be described as a closed, two-dimensional curved shape.

A circular region (area of a circle) is a part of a circle that consists of a circle and its interior region. A chord is part of a circle that can be described as the line segment joining any two points on the circle's circumference. Here, one notable thing is that the diameter is the longest chord of a circle which can be passed through the centre of the circle. Another important topic is the circle's diameter. The diameter of a circle is the distance across it passing through its centre point.

Students also learn about concentric and congruent circles. Concentric circles have a common centre, and the region between two concentric circles of different radii is called an annulus. Any two circles can be easily made concentric by inversion by picking the inversion centre as one of the limiting points. On the other hand, two circles are congruent if they are the same size. These sizes can be radius, diameter, or circumference.

Furthermore, students are taught concepts related to circumference. For example, the circumference of any circular form can be defined as a path or the limit that surrounds it. In simple words, the circumference can also be called the perimeter. Additionally, the relation between diameter and radius is also studied in this chapter. This concept is being discussed to learn how to relate diameter or radius to various other concepts and use it.

The area of a circle is the region that a circle occupies on a 2D plane. The formula for the area of a circle is given below, A=πr2
Where,
A = area; = 22/7 = 3.14; r = radius