Ranked Placements

Ok, so. I got placed in Bronze V. That would not be surprising since I was bronze V last season, but the thing is I won 7 games and lost 3 games. I still kind of understand that, but my other friend won the exact same amount of games as me and he got into bronze V, too. He was Bronze III. Is this broken or something? I really don't understand how we won that many and still got Bronze V. Like, is MMR that powerful as to place you in such a low rank with so many wins? Or am I just tripping and 7 wins and 3 losses is bad?