Question

Three red cards are numbered 1, 2, and 3 and the other three green cards are also numbered 1, 2, and 3. All of them are in a box. Randomly pick 2 cards one by one with returning before the second pick. Find the probability that they have the same number or the same color.

Answer 1

Explanation:

According to the information, first pick with returning make the question easy, it means that fist pick and second pick are independent events, we want to calculate the probability of same number or same color so 'or' means the addition method in statistics, from above second card has same number or same color decide the probability, not the first picked card,

P = P(same number) + P(same color) = 1/3 + 1/3 = 2/3

Or you can draw a tree diagram