Find the radius and circumference of a circle, whose area is :

(i) 154 cm²

(ii) 6.16 m²

The circumference of a circular table is 88 m. Find its area.

Find the area of a flat circular ring formed by two concentric circles (circles with same centre) whose radii are 9 cm and 5 cm.

The radii of the inner and outer circumferences of a circular-running-track are 63 m and 70 m respectively. Find :

(i) the area of the track

(ii) the difference between the lengths of the two circumferences of the track