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'Ip Dip' printed from http://nrich.maths.org/
"Ip dip sky blue! Who's 'it'? It's you!"
Have you ever used this rhyme to decide who is 'it' in a game?
If you were playing a game with one friend and you wanted to be chosen to be 'it', would you start the rhyme pointing at yourself or your friend?
If there were three of you, how would you position yourself so that you were sure you'd be chosen?
How about with four of you? Five ...? Six ...? Seven ...? Eight ...? Nine ...? Ten ...? And so on?
How would you predict where you should stand to be chosen for any number of players?