AB and CD are respectively arcs of two concentric circles of radii 21 cm and 7 cm and centre(see Fig.12.32).If `angleAOB=30^@`,find the area of the shaded region.

In given figure sectors of two concentric circles of radius 7 cm and 3.5 cm are shown. Find the area of the shaded region.

Area of /_\ABC=70cm^2 and CD=5cm . Find the area of the shaded region.

Two concentric circles are of radii 5 cm and 3 cm.Find the length of the chord of the larger circle which touches the smaller circle.

A sector from teo concentric circle is shown in Fig.14.If the radii of the circles are respectively 3.5 cm and 7 cm,find the area of the shaded region in the figure.

The area of an equilateral triangle ABC is 17320.5cm^2 .With each vertex of the triangle as center,a circle is drawn with radius equal to half the length of the side of the triangle(seeFig.12.28).Find the area of the shaded region.(use pi=3.14 and sqrt3=1.73205 )

In Fig.12.33.ABC is a quadrant of a circle of radius 20 cm and a semicircle is drawn with BC as diameter. Find the area of the shaded region.

A square OABC is inscribed in a quadrant OPBQ of a circle. If OA=14 cm, find the area of the shaded region.

A chord of a circle of radius 10 cm substends a right angle at the centre O. Find the areas of the sector. ( pi = 3.14 ).

In a circle of radius 21 cm,an arc subtends an angle of 60^@ at the centre.Find (i) the length of the arc

On a square handkerchief,nine circular designs each of radius 7 cm are made (see Fig.12.29).Find the area of the remaining portion of the handkerchief.