UPSC NDA Math Model Paper 2

Radius of a sphere is the distance between the centre of the sphere to any point on its surface.
Here the center is given to be (4, 4, -2) and the origin (0, 0, 0) is given to be a point on its surface.
∴r2=(4−0)2+(4−0)2+(−2−0)2 =16+16+4=36
⇒r=6