In a $ccp$ arrangement,what is the number of octahedral voids per atom?

$A$ compound forms a hexagonal close-packed $(HCP)$ structure. What is the total number of voids in $0.5 \ mol$ of it? How many of these are tetrahedral voids?

What is the full form of $fcc$?

$A$ compound is formed by elements $X$, $Y$, and $Z$. Atoms of $Z$ (anions) make $FCC$ lattice. Atoms of $X$ (cations) occupy all the octahedral voids. Atoms of $Y$ (cations) occupy $\frac{1}{3}$ rd of the tetrahedral voids. The formula of the compound is:

What is the percentage of space occupied by spheres of equal size in $hcp$ and $ccp$ three-dimensional arrangements?

The volume of the $HCP$ unit cell is