When heated above `916^(@)C`, iron changes, its crystal structure from body centred cubic to cubic closed packed structure. Assuming that the metallic radius of an atom does not change, calculate the ratio of the density of the bcc crystal to that of ccp crystal.

Explanation

In body-centered packing, the efficiency of packing is 67.92%.
In the cubic closed packing the packing efficiency is 74.02%
Let `d_(1)` be the density when packing efficiency is 74.02% and `d_(2)` is the density when packing efficiency is 67.92%.
`(d_2)/(d_1)=(67.92)/(74.02)=0.918`