Let us assume the edge length or the side of the cube = a

And the radius of each particle = r

The diagonal of a cube is always a

The relation between radius and the edge will be = 4r

Divide by root 3 we get, A

Total number of atoms in body centered cubic

Number of atoms at the corner

Number of atoms at the centre = 1

Total number of atoms = 2

The volume of the cubic unit cell

= side³

= a³

The volume of the occupied space

Packing efficiency

= 68%