A solid between A and B has the following arrangement of atoms Atoms A are arranged in ccp array

A solid between A and B has the following arrangement of atoms
Atoms A are arranged in ccp array Atoms B occupy all the octahedral voids and half the tetrahedral voids. What is the formula of the compound?
Answer - In a close packing, the number of octahedral voids is equal to the number of atoms and the number of tetrahedral voids is twice the number of atoms  Since all the octahedral voids and half the tetrahedral voids are filled there will be one atom of B in tetrahedral void and one atom in octahedral void corresponding to each A. Thus, there will be two atoms of B corresponding to each A.
Hence, formula of the solid is AB2