There are four balls in a hat: a blue one, a white one, and two red ones. Now I draw simultaneously two balls, look at them, and announce that at least one of them is red.
What is the chance that the other is red as well?
(In reply to re(4): Who's right
External agent? Ady, or whoever is looking at the balls, is telling us something about the pair he draws. We are asked to make a probability calculation from his statement.
You write "randomly chosen one
of the balls". You cannot assume just one ball is the basis of the decision when the problem uses "look at them
", which means that Ady looks at both balls to make his statement.