21-card trick - Numberphile
video description
1) No one claimed this is original. In fact, the description linked to that trick that all of you so gleefully mention.
2) The delivery is very different from Brady's, from start to finish. As most adults (and many kids) know, magic tricks are at least as much about misdirection as the sleight-of-hand. So magic fans should find it interesting for that alone.
3) Brady's not your daddy.
The criticisms remind me of all the Appple/Samsung/Star---- fanboys/girls competing for bragging rights. It really doesn't matter, unless this is what's important in your life. There's probably a bit of bigotry involved, but I don't want to make a big deal of it because those people like to scream as we've seen all too much lately. Like the Star Wars director said, some people need therapy. The bottom line is, we can learn something from everyone. The moment you stop acting like that, you're not as smart as you think, or can be.
Date: 2022-04-09
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Comments and reviews: 9
Panthror
A fun variation on this trick:
Count down 7 cards in a pile, then the next 7 cards you're going to alternate between 1/3 down and 1/3 up from the previous pile, so they lock in as if you were doing a riffle shuffle (1/3 overlap in the middle, the next 7 are going on top in a normal pile. You now have a pile with 4 cards sticking out the bottom and 3 sticking out the top. Grab the pile and squeeze the sides so that the pile is slightly bent. Now press the side with the 4 cards down on the table so the 3 cards on the other side rise, turn the pile upside down and press the side with 3 cards down on the table, turn once more (there should be 2 cards sticking out the bottom) and press down while exclaiming: -Was this your card? -
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A fun variation on this trick:
Count down 7 cards in a pile, then the next 7 cards you're going to alternate between 1/3 down and 1/3 up from the previous pile, so they lock in as if you were doing a riffle shuffle (1/3 overlap in the middle, the next 7 are going on top in a normal pile. You now have a pile with 4 cards sticking out the bottom and 3 sticking out the top. Grab the pile and squeeze the sides so that the pile is slightly bent. Now press the side with the 4 cards down on the table so the 3 cards on the other side rise, turn the pile upside down and press the side with 3 cards down on the table, turn once more (there should be 2 cards sticking out the bottom) and press down while exclaiming: -Was this your card? -
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Forest
To turn this in to a more general math question, we could ask, given M piles of cards, each containing N cards, what is the minimum number, S, of steps necessary to identify a selected card by this -stacking- technique? Will this stacking technique work for all possible values of M and N? Define the function S(M, N) in this way. So we know that S(3, 7) = 3. Is there a way of computing S(M, N) in terms of standard operations on integers, such as taking remainders or rounding off fractions, etc?
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To turn this in to a more general math question, we could ask, given M piles of cards, each containing N cards, what is the minimum number, S, of steps necessary to identify a selected card by this -stacking- technique? Will this stacking technique work for all possible values of M and N? Define the function S(M, N) in this way. So we know that S(3, 7) = 3. Is there a way of computing S(M, N) in terms of standard operations on integers, such as taking remainders or rounding off fractions, etc?
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Kristian
Why do it with 21 cards when you get the same results with 27, it splits evenly when doing 3 coloumns and I can make the card appear anywhere instead of doing the lame fake-choice thing letting them pick a card of group of cards and then you decide what you keep and what you throw away.
Plus most people have a lucky number under 27 that you can ask before hand, or you can in most cases also place it to be the date of today(doesn't work for 28. 29. 30. 31)
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Why do it with 21 cards when you get the same results with 27, it splits evenly when doing 3 coloumns and I can make the card appear anywhere instead of doing the lame fake-choice thing letting them pick a card of group of cards and then you decide what you keep and what you throw away.
Plus most people have a lucky number under 27 that you can ask before hand, or you can in most cases also place it to be the date of today(doesn't work for 28. 29. 30. 31)
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fudgesauce
This is literally the only card trick I know. I probably learned it when I was 12 and I'm now in my mid 50s. In my experience, nobody is really too surprised you can figure out which card is their during the first (sorting) phase. But their mind is blown when they think they picked their own card, instead of you forcing it. No kids figure out that you are forcing their selection, but about half of all adults catch on.
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This is literally the only card trick I know. I probably learned it when I was 12 and I'm now in my mid 50s. In my experience, nobody is really too surprised you can figure out which card is their during the first (sorting) phase. But their mind is blown when they think they picked their own card, instead of you forcing it. No kids figure out that you are forcing their selection, but about half of all adults catch on.
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education
No special manipulative skill needed for this golden oldie.
3x7 = 7x3
Sandwiching the chosen columns between the two others three times, automatically places the chosen card in the central (11th) position.
Making fans of three cards leaves the chosen card still in the central position.
Not worthy of a numerophile blog.
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No special manipulative skill needed for this golden oldie.
3x7 = 7x3
Sandwiching the chosen columns between the two others three times, automatically places the chosen card in the central (11th) position.
Making fans of three cards leaves the chosen card still in the central position.
Not worthy of a numerophile blog.
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tabaks
Although I knew about this trick for decades and have a fine understanding of its inner working, I am quite puzzled by a half-power reference to -underlying math- with only a few convoluted mentions. A failed opportunity to explain this to more than 3. 5 living humans.
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Although I knew about this trick for decades and have a fine understanding of its inner working, I am quite puzzled by a half-power reference to -underlying math- with only a few convoluted mentions. A failed opportunity to explain this to more than 3. 5 living humans.
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Kevin
My favorite way to do this trick is to poke the 2 cards sandwiching their card out the bottom of the deck, ask them if it's one of the 2 visible, and when they say no, hit the bottom of the deck on the table and it pokes their card up out the top.
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My favorite way to do this trick is to poke the 2 cards sandwiching their card out the bottom of the deck, ask them if it's one of the 2 visible, and when they say no, hit the bottom of the deck on the table and it pokes their card up out the top.
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Le
This trick is great right up until the very end, where it's just about confusing or -playing- the person you're showing the trick to. Kinda kills the magic, tbh. It should end with you finding the card after 3 column guesses and that's it.
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This trick is great right up until the very end, where it's just about confusing or -playing- the person you're showing the trick to. Kinda kills the magic, tbh. It should end with you finding the card after 3 column guesses and that's it.
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Mexie
Not sure if it's because of, or in spite of, me being both a mathematician and a magician, but I -HATE- mathematical magic tricks. (and I have to say that was also one of the worst examples of equivoque I've ever seen in a trick LOL)
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Not sure if it's because of, or in spite of, me being both a mathematician and a magician, but I -HATE- mathematical magic tricks. (and I have to say that was also one of the worst examples of equivoque I've ever seen in a trick LOL)
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