Des­pite the lack of sleep (I’ve been up for almost 24 hours), I’ve devised a fairly simple way to mem­or­ize a single card within a deck. It comes in the form a little trick you can play on friends into fool­ing them that you can count cards like Rain Man. It actu­ally works with simple addi­tion so most people should be able to do it with a little practise.

By apply­ing a unique value to each rank (Ace, 2, 3, 4, 5, and so on), you can determ­ine the total value of the entire deck:

Card	Value
Ace	1
2	2
3	3
4	4
5	5
6	6
7	7
8	8
9	9
10	10
Jack	11
Queen	12
King	13

Know­ing that the entire deck equates to 364, by remov­ing any one card, the deck’s value will lower by the value of that card. For example, if an Ace (1) is removed, the deck’s value will fall to 363.

So by get­ting a friend to remove a card, you can determ­ine their card by simply adding the remain­ing cards. It takes a few minutes and will only tell you the rank of the card, not the suit, so it’s prob­ably best to run through the deck again and take out the remain­ing three cards of that rank to “prove” you know what card they had. This trick works a treat but you can very eas­ily mess up your count, so be sure to take your time oth­er­wise you may end up with the wrong card.

If that’s too easy, you can always make things a little more dif­fi­cult by apply­ing a unique value based on the bumps/points its suit has:

Suit	Points/Bumps
Spades	1
Hearts	2
Clubs	3
Dia­monds	4

In prac­tise:

Card	Value
Ace of Spades	1
Ace of Hearts	2
Ace of Clubs	3
Ace of Diamonds	4
2 of Spades	5
2 of Hearts	6
2 of Clubs	7
2 of Diamonds	8

Note that with this sys­tem, the deck’s value will be 1378, as proven below:

A simple method to mem­or­ize each card might be to minus 1 from the rank, mul­tiply by 4, then add the bumps/points (for example: 4 of Dia­monds is 3 mul­ti­plied by 4, add 4; this equals 16).

With both sys­tems, it might be wise that whilst count­ing, to reset every time you hit 100 (for example: with a count of 96, a 6 would cause the run­ning count to fall to 2 instead of 102). This way, keep­ing count should be a lot easier. Good luck.