With the same centre O, draw two concentric circles of radii 3.2 cm and 4.5 cm.

With the same centre O ,draw two circles of radii 4 cm and 2.5 cm.

Draw a circle of radius 3.2 cm.

AB and CD are respectively arcs of two concentric circles of radii 21 cm and 7 cm and centre O. If ZAOB = 30^@ , find the area of the shaded region.

Draw a circle of radius 4 cm.

The area of a circle is equal to the sum of the areas of the two circles, whose radii are 5 cm and 12 cm respectively. Find the radius of the circle.

The adjoining figure shows two circles with the same centre. The radius of the larger circle is 10 cm and the radius of the smaller circle is 4 cm(a) the area of the larger circle (b) the area of the smaller circle (c) the shaded area between the two circles. ( pi = 3.14)

Find the area of the shaded region in Fig. 12.20, if radii of the two concentric circles with centre O are 7 cm and 14 cm respectively and angle AOC=40^@ .

In the following, give also the justification of the construction: Draw aline segment AB ol lengtb 8 cm. Taking A as centre,draw a circle of radius 4 cm and taking B as centre, draw another circle of radius 3 cm. Construct tangents to each circle from the centre of the other circle.

Draw a line segment AB of length 8cm. Taking A as centre, draw a circle of radius 4cm and taking B as centre, draw another circle of radius 3cm. Construct tangents to each circle from the centre of the other circle.

The area covered by two concentric circles is 770 cm^2 . The outer radius is 21 cm. Find the inner radius of circle.