This is a really old "magic" trick. I use quotes because it's actually just math, but all this is going to sound really familiar.
Take 21 cards and have a person select one at random. They can shuffle or do anything they want short of removing the cards, but at no point during this trick will you ever need to know their card so shuffling just makes it seem more impressive to them.
Place them in 3 piles, taking the first card in pile one, second in pile two, third in pile three, and the fourth back on the first pile and repeat till you run out of cards (1, 2, 3, 1, 2, 3, etc).
Ask which pile the card is in. Take that pile and put it in the middle. (aka, if their card is in pile 2, pick up pile 1 and place pile 2 on that, then pile 3 on top).
Repeat 3 times, always putting their card pile in the middle of the 3 stacks.
Count out 10 cards, the 11th card will always be their card. For added showmanship, you can spell out as you deal cards face down "H-O-C-U-S P-O-C-U-S" and then flip over their card, but obviously any 10 letter word works here.
This is a really old "magic" trick. I use quotes because it's actually just math, but all this is going to sound really familiar.
Take 21 cards and have a person select one at random. They can shuffle or do anything they want short of removing the cards, but at no point during this trick will you ever need to know their card so shuffling just makes it seem more impressive to them.
Place them in 3 piles, taking the first card in pile one, second in pile two, third in pile three, and the fourth back on the first pile and repeat till you run out of cards (1, 2, 3, 1, 2, 3, etc).
Ask which pile the card is in. Take that pile and put it in the middle. (aka, if their card is in pile 2, pick up pile 1 and place pile 2 on that, then pile 3 on top).
Repeat 3 times, always putting their card pile in the middle of the 3 stacks.
Count out 10 cards, the 11th card will always be their card. For added showmanship, you can spell out as you deal cards face down "H-O-C-U-S P-O-C-U-S" and then flip over their card, but obviously any 10 letter word works here.