Really confusing seemingly simple probability question Q. You toss 2 coins at the same time. They land on the floor. You don't look at the coins. Your friend tells you that at least one coin is heads. What is the probability of the other coin being tails? A1. [b]1/2 chance, or 50%[/b] The first answer is the common answer someone would say when asked this question. Because the outcome of one coin doesn't affect the other, the probability of the other coin being tails is simply 50%. A2. [b]2/3 chance, or 66.7%[/b] When 2 coins are tossed, there are 3 possible outcomes: H H - 1/4 H T - 1/2 T T - 1/4 Because it is given that at least one of the coin is heads, we can cross out the 'T T' outcome, so we are left with H H - 1/3 H T - 2/3 Which mak