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# Tag Info

## Hot answers tagged coins

42 votes
Accepted

### 68 coins with 100 weighings

It seems to me that there's a simpler solution than the one accepted above. Step 1: Step 2: Step 3: The point here is that
• 121k
36 votes
Accepted

### Simulating an unbiased coin with a biased one

One possibility: This works because: EDIT: Inspired by @trolley813's answer here is a way to recycle the rejected entropy:
• 21.3k
28 votes

### Coin Game with infinite paradox

OK, let's actually take this seriously. As others have said, this is the so-called St Petersburg paradox, and the reason it isn't really much of a paradox is that (1) an extra dollar matters much less ...
• 121k
25 votes

### 68 coins with 100 weighings

I see, it took me too long to fininsh my drawing, but let me present it as additional material to sousben's answer:
• 5,948
21 votes
Accepted

### Simulating a biased coin with an unbiased one

Yes, you can do it like this: Why does this work?
• 148k
21 votes
Accepted

• 619
16 votes
Accepted

### Coin removal problem

The row of coins can be fully removed if it has the following property: Proof: Solving strategy:
• 54.6k
16 votes

### Coin Game with infinite paradox

This gambling problem is the famous St. Petersburg paradox. It is a paradox because The one issue with this theoretical result is that it requires no upper limit on the possible winnings - if you ...
• 4,878
16 votes
Accepted

### A puzzle about two coins of total value of 15 cents, one of which is not a nickel. Is it correct at all?

If the puzzle had said that neither coin was a nickel, a solution could have consisted of: But with the puzzle as actually posed, your answer was correct, and the person who responded to you was both ...
• 7,250
14 votes
Accepted

### How will Y lose the game?

Generalization. There are $K$ coins on the table and one player can pick as many as M coins at once.
• 18.2k
13 votes

### How will Y lose the game?

Using winning/losing position analysis you can tell that the correct move is to take: You can work this out iteratively. If you have 1 coin and it is your turn you will obviously lose. Thus 1 is a ...
• 1,825
11 votes

I would pay
• 211
10 votes

### 68 coins with 100 weighings

Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Then This makes a total of:
• 2,586
9 votes
Accepted

### Five Men and Four Coins Puzzle

For my answer I'm considering the sides of the coin to either have a star or be blank for ease of writing. I also will write out the number for peoples name, and use the character for guesses to try ...
• 126
9 votes

### Sand Castle Builder Glass Ceilings Puzzle

There are several physical versions of this puzzle: (Elephant) Spinout, by thinkfun: The Brain, by Mag-Nif: and the traditional Chinese Rings puzzle: The solution is based on the Binary Gray Code. ...
• 54.6k
8 votes

### Coin Game with infinite paradox

There are several nuances to this question. First of all, it asks how much you are willing to pay, not what price is fair. Second, you have to understand, that even if a game is fair, that does not ...
• 2,963
8 votes

### Coin Game with infinite paradox

I would not pay anything. I would not play. I would encourage you to not play. Are you doing okay? I'm willing to help you out of you need help. I would offer you a hug. You are my best friend, ...
• 2,081
8 votes
Accepted

### 12 coins problem but you can't understand the scale

This was quite a fun twist on weighing puzzles. The fact we don't know what the scale outputs mean requires us to, as part of our weighing procedure, decipher the scale's output. Luckily, we only need ...
• 492
7 votes

### How will Y lose the game?

X should pick up Because Examples:
• 2,019
7 votes

### Five Men and Four Coins Puzzle

The first toss is a star (*) or not (-). Mr Two immediately loses. The second flip can be either, so we have **, *-. -*, or --. Also on that flip, The third and fourth flip and To sum:
• 5,905
7 votes
Accepted

### The Dollar Bill

One Dollar One dollar Which should look something like the following image:
• 226
7 votes

### Simulating an unbiased coin with a biased one

A straightforward answer (actually, a generalisation of loopywalt's answer): Example:
• 11.3k
7 votes

### Simulating a biased coin with an unbiased one

This works because
• 5,190
6 votes
Accepted

### Riffing off of Dudeney

First puzzle in 4 moves: Second puzzle in 5 moves: The way I solved these is I do not know if these are optimal. I would not be surprised if shorter solutions are possible.
• 54.6k
6 votes

• 231
6 votes

### 12 coins problem but you can't understand the scale

Once you can identify which symbol means "equal", this reduces to the original problem. That is because if you follow a valid strategy assuming that A means "left heavier" and B ...
• 3,071
6 votes
Accepted

### Sand Castle Builder Glass Ceilings Puzzle

N=1 N=2 N=3 N=4 N = 5 N = 6 Formula for any N:
• 1,861

Only top scored, non community-wiki answers of a minimum length are eligible