In a close-packed lattice,the number of tetrahedral voids compared to the number of octahedral voids is:

The volume of the $HCP$ unit cell is

The number of octahedral and tetrahedral holes respectively present in a hexagonal close packed $(hcp)$ crystal of $X$ atoms are

$A$ compound is formed by two elements $X$ and $Y$. The element $Y$ forms a cubic close-packed $(CCP)$ arrangement and the atoms of element $X$ occupy one-third of the tetrahedral voids. What is the formula of the compound?

The maximum radius of a sphere that can be fitted in the octahedral hole of a cubical closed packing of spheres of radius $r$ is $..............$ $r$.

The molecular formula of a crystal is $AB_2O_4$. Oxygen atoms form $ccp$ lattice. Atoms of $A$ occupy $x \%$ of tetrahedral voids and atoms of $B$ occupy $y \%$ of octahedral voids. $x$ and $y$ are respectively: