Card probabilities ......

Suppose you are told that the ace of spades is not at the top of a standard card deck.
What is the probability that the ace of diamonds is at the bottom of the stack ?

the ace of spades has 51 positions available (since it's not at the top)
having placed it somewhere, there are 51 positions available for ace of diamonds, so

Pr = P(ace of spades not at bottom)*(Pace of diamonds at bottom)

= 50/51 *1/51 = 50/51² <--------

1 - 1/51
= 50/51

(50/51)/51
= 50/2601

1/52 I think.