RD Sharma Solutions for Class 7 Chapter 21 “Mensuration-II”. In this chapter, we will discuss problems on the circumference and area of a circle. We will also discuss problems on an area of a segment and a sector of a circle. Mensuration – II (Area of Circle) discusses the topic of the circular region, chord of a circle, diameter, concentric circles, congruent circles, the circumference of a circle, the relation between diameter and circumference, the definition of number pi and area of the circle.