Royal Arm Wrestling

How many arm-wrestles will there be in the royal arm wrestling championship?
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The Kings of Clubs, Diamonds, Hearts and Spades, and their respective Queens, are having an arm wrestling competition. Everyone must wrestle everyone else, except that no King will wrestle his own Queen. How many wrestling bouts are there?

 

If you liked this problem, here is an NRICH task which challenges you to use similar mathematical ideas.