A statistics teachers from another class in my high school had a rock-paper-scissors game at the end of the year. But the catch was, you had to bet your mark in

A statistics teachers from another class in my high school had a rock-paper-scissors game at the end of the year. But the catch was, you had to bet your mark in the game. If you won, he adds 1% to your final mark. If you lost, you lose 1% from your final mark. Of course, there was a statistics lesson at the end to be learned from it. Even though it appears to be that you both have an equal chance to win (both of you have 33%), why would someone offer you an equal game unless he had some sort of advantage that you aren't aware of? The trick was to look at the opponents hand while it was still going down. If you're throwing rock or scissors, your hand will be clenched the whole way down. If you were throwing paper, you will probably open your hand halfway down your throw. So when he sees you opening your hand, midway he will change his to scissors. And if it doesn't stay open, then he will use rock, since between rock and scissors, rock will either win or tie. It required a bit of hand dexterity, but he practiced wing-chun, so it wouldn't have been a problem for him. Of course, the trick doesn't work 100% of the time, so you were allowed a maximum of two tries discounting ties, preventing kids from getting winning streaks. It was a pretty interesting lesson, and I was glad that I skipped my statistics class to go to his.