Question

Each house number on a street has 2 non-zero digits that are different. What is the probability that the second digit is less than 3, given that the first digit is less than 3?

Answer 1

If the 1st is a 1 or 2, the P(2nd < 3) = 1/8
if not, then P(2nd < 3) = 2/8
so, ...