Especially Lime
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2 answers
9 votes
247 views
12 coins problem but you can't understand the scale
3 votes

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 ...

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3 answers
-2 votes
240 views
how much does my bag weigh
4 votes

MichaelMaggs' answer is generally reasonable but misses one vital point:

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7 answers
32 votes
2k views
Two out of a dozen cartons have Easter eggs. Two people try to find one Easter egg carton, each using a different strategy. Who is expected to win?
1 votes

Consider the following cases: There is an egg in A There is no egg in A, but exactly one in B or E There is no egg in A, B or E, but exactly one in C or I There is no egg in A, B, C, E or I, but ...

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2 answers
7 votes
502 views
A Sudoku With A Trick
2 votes

I must have missed the trick somehow. You can fill in a few 1/2/3/4s straight away. After that there are only two spaces left in the top right, which are 8/9 in some order. I tried the one that seemed ...

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4 answers
6 votes
399 views
How to get the least number of flips to a plastic chips to get a certain figure?
13 votes

Suppose there are $n\geq 3$ chips. It's easy to see that $n$ moves is possible, making each move exactly once (this flips each chip three times). Since making the same move twice cancels out, any ...

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5 answers
19 votes
980 views
Basic Numerical Boggle
4 votes

A slight improvement to Misha Lavrov's answer. Unfortunately I don't think this can be pushed any further:

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15 answers
26 votes
7k views
Is this a good question for an IQ test?
Accepted answer
17 votes

I disagree with most of the other answers - I think it is a better question than most actual IQ test questions. The point is that if you haven't seen something like this before, then whether you're ...

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5 answers
13 votes
2k views
Maximise your gold!
0 votes

Suppose there are $R$ red lamps and $150-R$ blue.

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3 answers
5 votes
397 views
Playing the Square Chess
4 votes

Suppose black passed. White could easily win in three moves: c3 forcing e3, then d4 threatening to create either of two squares. White could also use the same tactic starting with e3, c7 or e7. If ...

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4 answers
6 votes
232 views
Find a sufficient passcode
0 votes

Well, the most obvious explanation for Ms Salem is that she rejects There are probably several possibilities for Mr Spencer, but I can't find one that seems as natural as the above. Certainly it's ...

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1 answers
6 votes
253 views
The sadistic chieftain and the lethal truel game
Accepted answer
2 votes

Suppose that the guns, and order of turns, have already been determined. There are only two plausible strategies for the player with the bad gun: either they always shoot at the player with the good ...

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3 answers
1 votes
217 views
Blood Type Puzzle 2: Am I Pure Blood?
2 votes

As JNF says, your mother must have AB parents and be BB herself. Applying the final point directly to your father, before taking into account information from your own blood type your priors for his ...

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8 answers
4 votes
754 views
Two doors, two guards, and two keys
2 votes

Here's a question which I think works. Explanation: (Note: I came up with this without reading the extra "warming up" section, so my question doesn't produce the exact same table that you had, but ...

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1 answers
4 votes
265 views
London Underground puzzle
Accepted answer
5 votes

I think this works. The line used between each two stops is in brackets. Oxford Circus (Victoria) Green Park (Picadilly) Picadilly Circus (Bakerloo) Charing Cross (Northern) Embankment (District) ...

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2 answers
18 votes
2k views
Blind Person Ball Game
Accepted answer
17 votes

elias's strategy for is optimal. To see this, note that

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4 answers
12 votes
2k views
A Chess Lock Puzzle?
Accepted answer
14 votes

I think there's a quicker way to do it. for 12 moves.

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5 answers
107 votes
15k views
Mate in 0 moves
82 votes

I see Evargalo has found the right answer, but the first thing that occurred to me was

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5 answers
12 votes
5k views
Hard 4x6 chocolate bar Riddle
22 votes

If cuts are allowed to meet the perimeter between the start and end, as in Peregrine Rook's answer, the best you can do is You can't do it with fewer. Of course, if cuts aren't allowed to hit the ...

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2 answers
4 votes
314 views
Is there a definite answer to this Minesweeper puzzle? If not, which square has the best chance of being safe?
Accepted answer
2 votes

hexomino is correct that there's not a safe way to proceed, but the heuristic doesn't give the right probabilities for the remaining squares. Looking at the top five unknown squares, there are five ...

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6 answers
5 votes
797 views
You meet Yessayer, Nosayer, Truther, Liar
1 votes

Here's a method with three questions that is less artificial than boboquack's solution. I'll assume there are four people in a line, (left)ABCD(right). First, tell everyone "I'm thinking of a ...

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1 answers
12 votes
248 views
Re order the clues
Accepted answer
11 votes

They are all In order

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2 answers
7 votes
947 views
Cross the river with a small (4 spaces) boat
2 votes

The reverse of Beastly Gerbil's solution also works: These are the only two possibilities.

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5 answers
11 votes
793 views
Can the idiot's route be less expensive than the genius' route?
4 votes

Artur's proof is very nice. I did it a different way. First, note that it is sufficient to prove that for any C it is impossible for the genius to take more steps of cost at least C than the idiot. So ...

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15 answers
50 votes
7k views
Find the identity of the four troll brothers
0 votes

It can actually be done in You need at least that many because Here is a strategy which achieves this.

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6 answers
7 votes
2k views
Knights and knaves at a party
1 votes

It's impossible to tell. Daniel's question "Are you from the same tribe as your spouse?" is one possibility for the amazing question (even though he got convinced otherwise in the comments). Two yeses ...

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