56. The Heads/Tails Con
class: tweener | impressiveness: 4/5 | factors: complicated logic, precise instruction | requires: collection of quarters, an intelligent target | watch full episode
This one might sound a little heady when you learn it, but trust me: it’s much easier in practice, and the effect seems impossible. Just do a few trial rounds with a friend before you try it on strangers at the bar.
How it Looks: Start with a fistful of quarters spread out on the table, arranged in a random assortment of “heads” and “tails.” You turn around, and ask her to flip over any coin she wants. Then ask her to do it again. And again. Ask if she wants to go again, then ask one more time if she wants to flip another over. It doesn’t matter how many times she flips over coins, as long as you know how many coins were flipped.
Once she’s satisfied that there’s no way you could know the arrangement or positions of any of the quarters, have her choose any one coin to cover up with her hand.
When you turn back around, just by looking at the exposed quarters, you’ll know instantly whether her covered coin is “heads” or “tails.”
The Method: Surprisingly enough, it’s super simple. When you first lay out all the coins, count how many of them are heads-up and remember whether it’s an even or odd number. Make sure you count accurately, because this first count is important.
After you turn around, every time she says she’s flipping over a coin, you flip your mental running count from “odd” to “even” or from “even” to “odd.” This can get confusing once you’re a couple of beers in at the bar, so I recommend using your fingers to keep track under the bar where she can’t see. Hold two fingers out for even, one finger for odd, and make sure to change them with each coin flip.
Once she says she’s done flipping coins, note whether you’re currently on EVEN or ODD.
Read that again: If you’re thinking “odd” when she stops, there are now an odd number of heads on the table. If you’re on “even” when she stops, then there are an even number of heads.
So when you turn around, count all the heads-up coins you see.
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If the number of heads-up coins you count matches your running count: that means she’s hiding a tails. (In other words, if you expected an even number, and you see an even number, she must not be hiding another heads-up coin)
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If the number of heads-up coins you count does not match your running count: then she must be hiding the last heads-up coin.
It’s SUPER important that you practice your tempo and phrasing during the trick to make sure you absolutely know how many coins are flipped over. If there’s any ambiguity, your running count might get off and leave you looking like a chump at the reveal.