The diameter of one sphere is 21 cm, and the diameter of another sphere is 14 cm, the ratios of their curved surface areas is
9 : 4
3 : 2
4 : 9
2 : 3
If the surface area of a sphere is 616 cm2 its diameter is
A cube is 7 cm on an edge and another cube is 14 cm on an edge. The ratios of their curved surface areas are