Try this on one of your "smarter" friends.

Use the spot-cards from Ace to Six and arrange them on the table like this:

. . . $\displaystyle \begin{array}{cccccc}A\diamondsuit \\ 2\diamondsuit \\ 3\diamondsuit \\ 4\diamondsuit \\ 5\diamondsuit \\ 6\diamondsuit \end{array}

\begin{array}{cccccc}A\clubsuit\\2\clubsuit\\3\clu bsuit\\4\clubsuit\\5\clubsuit\\6\clubsuit\end{arra y}

\begin{array}{cccccc}A\heartsuit\\2\heartsuit\\3\h eartsuit\\4\heartsuit\\5\heartsuit\\6\heartsuit\en d{array}

\begin{array}{cccccc}A\spadesuit\\2\spadesuit\\3\s padesuit\\4\spadesuit\\5\spadesuit\\6\spadesuit\en d{array}$

You and your victim will take turns removing cards and keep a running total.

The first to reach $\displaystyle 31$ (without going over) wins the game.

If you play first, take a $\displaystyle 3$.

Whatever he takes, take the "7-complement".

. . If he takes a 5, take a 2. If he takes an Ace, take a 6.

The totals (after your turn) will be: $\displaystyle 3,\,10,\,17,\,24.$

. . And after his next move, you will reach 31 with your next move.

If he plays first, try make the total 3 or 10 as soon as possible.

. . And proceed as described above.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

So far, this game is not very impressive, is it?

Here's where the swindle comes in.

Eventually he will catch on that you always start with a 3

. . and he may discern the rule of the 7-complement.

(Better yet, have a "shill" take him aside and explain the winning strategy.)

Confident that he will win, he may even raise the stakes

. . (not that I encourage gambling, mind you).

He begins by taking a3.

You take a3. .He will take a4. .Total: 10

You take another3. .He takes another4. .Total: 17

You take a4. .He takes a3. .Total: 24

You take a4.

He will reach for a 3 and find to his horror thatthere are no more 3's!

He must either go over 31 and lose . . . or go under 31 and allow you to win.