The probability of finding an adjacent pair in a deck
David Singmaster · The Mathematical Gazette · 1991
Robert Harbin, in Waddingtons Family Card Games , gives an item called Prediction. You ask a friend to name two values of cards and to shuffle a deck. Then you bet that his two values will come up together as the deck is turned over. Harbin says he has worked out the odds as 32 to 19 in favour of success— “but I could be wrong. See what you make it.”