I'm having a debate with a friend and we're trying to decide the correct answer to a question someone brought up. I'm sure you guys in this group will know the answer lickity-split.
There is a single can with a marble in it. The marble is either red or green, but is otherwise identical. There's an equal chance of a marble being each color. Someone throws in a green marble (same size and weight as other marble). Without looking, a person takes out a marble. What is the chance that it will be green?
We've arguing over whether it's 3 in 4 (75%), or 5 in 6 (83%).