Actually, that would only be true if it read "There were 10 guys for every 1 guy.". Since the "1" was not there, the minimum would have to be 121. The reason this is, if there were 10 guys for every guy, then those 10 guys would each have 10 of their own, which is 110, and once he walked in and there were 10 guys for him as well, that would make 121.