A standard deck of playing cards has cards divided into four suits (clubs, diamonds, hearts, spades). Each suit consists of nine "number cards," each containing a different number from to , and four "face cards" that include a jack, a queen, a king, and an ace. In the game of Cribbage, points are earned if you can combine two cards that sum to . Jacks, queens and kings each have a value of , aces each have a value of , and all number cards have a value of the number shown. How many different unordered pairs of two cards sum to in a standard -card deck?

Coolio May 31, 2020