Busted ranking system.

I'm really confused about the ranking system, on an alternative account I made an account with my friend. We both played League together on this(can't even call it a smurf because my main is only silver) account and we ended up getting to level 30 within a day from each other. We go on to play our placement games and he wins 1 of 10 games and I win 7 of my 10 games. He got placed in Silver three, and I got placed in Bronze 3. How the hell does that make any sense at all?