Question

A card is drawn from a standard deck of 52 cards and then a second card is drawn without replacing the first card. If we know that the second card is a spade, what is the probability that the first card is a spade? 

Answer 1

There are 13 spades in a standard deck. We know that the second card is spade, so there are only 12 spades left in the remaining deck of 51 cards. Hence the probability is equal to 12/51.