1.12. A circle of radius $R$ is divided by two concentric circles into three figures of equal area. Find the radii of these circles.
1.12. D e f i n i t i o n. Use the equalities $\pi R_{1}^{2}=S$, $\pi R_{2}^{2}=2 S, \pi R^{2}=3 S$, where $R_{1}$ and $R_{2}$ are the radii of the smaller and the middle circles, and $S$ is the area of the smaller circle.

A n s w e r: $R_{1}=\frac{R \sqrt{3}}{3}, R_{2}=\frac{R \sqrt{6}}{3}$.