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Find the radius of a sphere whose surface area is 154 $${cm}^{2}$$.

Let the radius of the sphere be r.
Given :
Surface area of sphere = 154 $$cm^2$$
$$\Rightarrow$$ $$4 {\pi} {r}^2 = 154$$ $${cm}^{2}$$
$$\Rightarrow$$ $${r}^2 = \frac{154 × 7}{4 × 22}$$ $${cm}^2$$
$$\Rightarrow$$ $${r}^2 = \frac{7 × 7}{2 × 2}$$ $${cm}^2$$
$$\Rightarrow$$ $$r = \frac{7}{2} cm = 3.5 cm$$

$$\therefore$$ the radius of the sphere whose surface area is 154 $${cm}^{2}$$ is 3.5 cm.