Question

where is centre of mass lies radius and mass are same of three con-centric sphere

Answer 1

Welcome to OpenStudy. In a sphere, the center of mass will be in the center. The radius can be found using the formulas
\[c=2\pi r\]
\[V=\frac{ 4 }{ 3 }\pi r ^{3}\]

This is all I can understand from your question.