A sphere of diameter 12.6 cm is melted and cast into a right circular cone of height 25.2 cm.

(a)  6.3 cm
Let r cm be the radius of base of the cone.
Volume of the sphere = volume of the cone

$\Rightarrow \frac{4}{3} \pi \times(6.3)^{3}=\frac{1}{3} \pi \times r^{2} \times 25.2$

$\Rightarrow r^{2}=\frac{4 \times 6.3 \times 6.3 \times 6.3}{25.2}=39.69$

$\Rightarrow r=\sqrt{39.69}=6.3 \mathrm{~cm}$