The height of a right circular cylinder is 10.5 cm.

Let $r$ be the radius of the circular cylinder.

Height, $h=10.5 \mathrm{~cm}$

Area of the curved surface, $S_{1}=2 \pi r h$

$S$ um of the areas of its two circular faces, $S_{2}=2 \pi r^{2}$

According to question:

$3 S_{2}=2 S_{1}$

$3 \times 2 \pi r^{2}=2 \times 2 \pi r h$

$6 r=4 h$

$3 r=2 h$

$r=\frac{2}{3} \times 10.5 \mathrm{~cm}$

$=7 \mathrm{~cm}$