Three mates, Chris, Aaron and Pete spend a day together at the racetrack. By the last race of the day they're down to their last $10. They decide to put it all on a trifecta bet. To select their numbers they decide to go with the lengths of their respective members.
Chris chooses 9.
Aaron chooses 7.
And Pete chooses 2.
They place their bet and as luck would have it they win the trifecta; a cool $10,000. They collect their winnings and then argue over how to split the prize.
Chris claims that as he contributed the 9 he is entitled to half the winnings.
Aaron, says that in that case he's entitled to 7/18 of the prize.
"Hang on", says Pete. "You blokes owe me! If I hadn't had an erection at the time, we'd have bet on 9, 7 and 1."