is there an equation to determine how many entries to enter in a limited entrants sweepstakes to skew the odds?

Question

Skew the odds in my favor. I know that sweepstakes winners are chosen randomly and I still might not win if I enter many entries. I just want to know how many entries I should enter to have a decent chance of winning

Answer 1

It depends on what you mean by a decent chance. If you make n entries and there are N total entries, your chance of success in a purely random drawing is n/N

Answer 2

If you buy half the tickets, and if a winner always drawn, then you have a 50% chance.