posted by Glare .
A card is drawn from an ordinary pack of playing cards and a person bets that it is a spade or a king.What are odds against his winning this bet?
P(spade) = 1/4
P(king) = 1/13
P(spade v king) = P(spade) + P(king) - P(spade ^ king)
= 1/4 + 1/13 - 1/4 * 1/13