$A$ compound is formed by elements $A$ and $B$. Element $B$ forms an $HCP$ lattice,and element $A$ occupies $2/3$ of the tetrahedral voids. What is the formula of the compound formed by $A$ and $B$?

If a compound (oxide) has an $hcp$ arrangement and the cations $M$ occupy two-thirds of the octahedral voids,the formula of the compound is:

In a compound,atoms of element $Y$ form $ccp$ lattice and those of element $X$ occupy $2/3$ of tetrahedral voids. The formula of the compound will be

In which of the following crystals are all the tetrahedral voids occupied?

$A$ compound is formed by atoms of $A$,$B$ and $C$. Atoms of $C$ form $hcp$ lattice. Atoms of $A$ occupy $50\%$ of octahedral voids and atoms of $B$ occupy $\frac{2}{3}$ of tetrahedral voids. What is the molecular formula of the solid?

Find the number of tetrahedral voids per atom in a crystal lattice.