Simple Graph Set Question

23 Views Asked by At

Prove that in any set $S, |S| = 3k$ there exist $2^k$ subsets $V_i$ such that $|V_i| = 0 \mod 3$ and the cardinality of any intersection is $0 \mod 3$ as well.

1

There are 1 best solutions below

0
On BEST ANSWER

Divide the elements of $S$ up into $k$ blocks of three. Then how many ways are there to select a collection of blocks? (Hint: you're effectively just selecting a subset of $\{ \text{the $k$ three-sized blocks} \}$.)