Metallic solids ‘A’ and ‘B’ crystallize into ccp and bcc structures respectively. Ratio of atomic radii of B to A is 1.732 : 1.414. Ratio of densities of unit cells of A to B will be (Molar masses of A and B are 69 grams and 23 grams respectively)

ρ(density of unit cell) = ZMNAa3Given ZA=4(ccp); MA=69g; ZB=2(bcc); MB=23g Radius of 'A' =a22 aA=22rA Radius of 'B' =3a4 aB=4rB3 ρAρB=ZAMAaA3×aB3ZBMB         =4×69162rA3×64rB3332×23 =4×69×64×rB3162×2×23×3×3×rA3=4×69×64×1.7323162×2×23×3×3×1.4143 =4×69×64×33162×2×23×3×3×22=6