A right circular cone has a base radius of 10 cm and a slant height of 25 cm, then what is the radius of the largest possible sphere inside the cone?
1
\(10\sqrt {\frac{3}{7}} cm\)
2
\(\frac{{10\sqrt {21} }}{3} cm\)
3
\(10\sqrt {\frac{3}{5}} cm\)
4
\(10\sqrt {\frac{7}{3}} cm\)