This isn't about math, don't worry! This was a game I played on another forum a while back. Someone starts by naming a person, place, or thing (plant, object, animal, etc) and the next person has to name a person, place, or thing that is in common with the first post. You just keep going from there.
Example:
user one - "Pirate"
user two - "Johnny Depp played Jack Sparrow, a pirate"
user three - "Song Sparrow, a type of bird"
Let's start with:
Tiger Lilly