Coin puzzle: How do you make a circle of 6 coins from two rows in only 3 turns?

boing
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Originally published at: https://boingboing.net/2018/05/03/coin-puzzle-how-do-you-make-a.html

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It only takes 2 moves.

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That’s against the rules. You have to only move a coin into a position where it touches two other coins.

What may trip some people up is is they assume the reverse is true: a move must not leave a coin touching only one other coin. This isn’t a stated rule, and totally allowed. It’s only the coin you’re moving that must maintain contact with 2 coins. Tricky!

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I can’t watch the video right now and assume there’s some explanation of why this doesn’t count, but I mean…

ooo
.ooo

.o
ooo
.oo

.oo
o…o
.oo

?

edit-while I’m at it, is pushing a different coin with the coin you’re moving against the rules? cause I bet I could do it in one move. I should probably stop talking until I can watch the video.

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Wut? Why? Roll the upper right coin clockwise around until it touches the two at that end of the bottom row, then pull the (now) center coin out to fill the gap in the edge and complete the circle - done!

(ETA: for cool ASCII graphics, @summanulla is doing this same thing from the opposite corner and direction.)

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I just wandered off to watch the video without sound to try to figure this out, it looks like there’s a rule against touching any other coins while you’re moving stuff or something like that, so the one we’re thinking doesn’t count because it pushes the side ones out of the way when moving the center out.

I really wish we got text versions of puzzles when they get posted. I love puzzles, but they’re always in video or audio form.

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:point_up_2::+1:

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Not trying to humblebrag, but I saw the solution to this so quickly and painlessly that if it’s supposed to be hard I’m seriously concerned I might be a replicant.

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is it cheating to notice the coins have all different faces? kinda ruined ( or solved i guess ) the which ones move where aspect of it.

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Describe in single words only the good things that come into your mind about… your mother.

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don’t go past 2:37 unless you want to see how it’s done.

*goes directly to 2:37 *

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It’s surprisingly tough. I figured it out by reasoning backwards. It’s obvious what the last move is.

You can’t pick it up, and being surrounded by 5 coins, it’s locked in. You can’t move that center coin anymore.

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