Question

six cards are numbered 1 1 6 7 11 and 12 cards are chosen without replacement until a card number 1 is chosen. find the probability that this happens before the third card is chosen

Answer 1

"Before the third card is chosen" means a 1 is chosen as either the first card or second card.

Probability of 1 being chosen as first card = 2/6.

Assuming that the first card was not a 1, the probability of 1 being chosen as a second card = 2/5.

Either-or probabilities are found by adding the individual probabilities.