Math 241 Stuff

Suppose that an ordinary deck of 52 cards is shuffled and the cards are then turned over one at a time until the first ace appears. Given that the first ace is the 20th card to appear, what is the conditional probability that the 21st card is:

1. ace of spades?
2. two of clubs?

Instructor Solution

$$ \begin{aligned} C &= 1+x \\ D &= a \end{aligned} $$