How many products does this reaction yield?
The expected products of mono-chlorination of 2,4-dimethylpentane are depicted in following scheme:



The substrate has 12 primary hydrogens (on 1-,1'-, 5-, and 5'-methyl groups),  2 secondary hydrogens (on 3-methylene group),  and 2 tertiary hydrogens (on 2-, and 4-methine groups), as numbered in the scheme. Altogether, total of 3 different hydrogens are present, therefore, 3 different mono-chlorinated products are possible as sketched in the bottom boxes of the scheme. Although 1- and 1'-methyl groups (and 5- and 5'-methyl groups as well) are equivalent in the structure, mono-chlorination of each would give different stereoisomer (strictly speaking, enentiomers). Therefore, counting stereoisomers, you should get total of 4 different products.