$\begin{align}  & \text{Surface area of a sphere}~=A=4\pi {{r}^{2}} \\ & 154=4\times \tfrac{22}{7}\times {{r}^{2}} \\ & {{r}^{2}}=\frac{154\times 7}{4\times 22}=\frac{49}{4} \\ & r=\sqrt{\frac{49}{4}}=\frac{7}{2}=3.50cm \\\end{align}$