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Coin Tossing Games

You and I play a game involving successive throws of a fair coin. Suppose I pick HH and you pick TH. The coin is thrown repeatedly until we see either two heads in a row (I win) or a tail followed by a head (you win). What is the probability that you win?

Win or Lose?

A gambler bets half the money in his pocket on the toss of a coin, winning an equal amount for a head and losing his money if the result is a tail. After 2n plays he has won exactly n times. Has he more money than he started with?

Thank Your Lucky Stars

A counter is placed in the bottom right hand corner of a grid. You toss a coin and move the star according to the following rules: ... What is the probability that you end up in the top left-hand corner of the grid?

Mathsland National Lottery

Age 14 to 16
Challenge Level

What is the probability that the first number drawn matches one of your choices?
What is the probability that the second number drawn also matches one of your choices? 
What is the probability that the first two numbers drawn match two of the numbers you have chosen?

Does it help to draw a tree diagram?