number of baseball teams
According to NBC's Ask Liz column, MLB says an average of 65 balls are used per game. There are 30 teams playing each other in 162 games each. So there are (15 x 162 = 2,430) games per season, (you have to divide the total number of teams by two, since each game has two teams in it). That equals: (2,430 x 65) baseballs used per season, which totals 157,950 baseballs used during games per regular season.