The formula for finding volume of a cone 1/3pi x r^2h. the volume of a cone is 300 cm^3 and the height of the cone is 10 what is the approximate radius of the cone

In the figure below, ∠dec ≅ ∠dce, ∠b ≅ ∠f, and segment df is congruent to segment bd. point c is the point of intersection between segment ag and segment bd, while point e is the point of intersection between segment ag and segment df. the figure shows a polygon comprised of three triangles, abc, dec, and gfe. prove δabc ≅ δgfe.