The area enclosed between two concentric circles is 770 sq. cm given that the radius of the outer circle is 21 cm. Find the radius of the inner circle.

The area of a circle is 1386 cm^2 . Find the circumference of the circle.

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

A circle is inscribed in a square. If the radius of circle is 5 cm. Find the perimeter of the square.

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.