Q10 of 31 Page 178

The radii of two concentric circles are 4 cm and 3 cm respectively. The area enclosed by the two circles is:


The radius of the smaller circle AB = 3 cm


And radius of the larger circle AC = 4 cm


The area enclosed between two concentric circles = Area of the larger circle – area of the smaller circle


∵The area of a circle = πr2


⇒ Required area = πR2 - πr2


⇒ Required area = π (R2 - r2)


Using (a+b)(a-b) = a2 - b2


⇒ Required area = π (R+r)(R-r)


More from this chapter

All 31 →
8

The radius of a circular grass field is 35 m. There is a 7 m wide path all around it. Find the area of the path.

 9

The area enclosed between two concentric circles is:

 1

In a circle of radius 7 cm, an arc subtends an angle of 60° at the centre. Find the length of the arc.

 2

A sector of a circle of radius 10.5 cm contains an angle of 45°. Find the area of the minor sector.