I came across this and wanted to see what everyone's thoughts were. The website I found it on actually had the answer too, but I figured I'd post it a little later so everyone who wanted to could try it first—-unless they decide to try to find the website haha

This is a magic trick performed by two magicians, A and B, with one regular, shuffled deck of 52 cards. A asks a member of the audience to randomly select 5 cards out of a deck. The audience member — who we will refer to as C from here on — then hands the 5 cards back to magician A. After looking at the 5 cards, A picks one of the 5 cards and gives it back to C. A then arranges the other four cards in some way, and gives those 4 cards face down, in a neat pile, to B. B looks at these 4 cards and then determines what card is in C’s hand (the missing 5th card). How is this trick done?