A Deceptively Hard Puzzle
The digits from 0 - 9 are separated into 3 groups: A (0, 1, 2, 3); B (4, 5, 6); C (7, 8, 9). Digits are selected at random (no repeats) until the numbers from an entire group are chosen. What is the probability that group “A” will be selected?
It seems like there ought to be a simple “trick” to solving this, a clever way of looking at it that will make it easier to solve, but if there is, we (the commenters on that thread) haven’t found it yet!