All Questions

Dear PSE users and moderators, I’m new here in PSE, but I really need your help. There was this person who gave me a black envelope consisting 10+1 pages of puzzles, and also a scribble saying: “Find ...

Is there a sequence of moves that can be repeated over and over again which can solve any legal position the Rubik's Cube? If so what is it, and if there's more than one, what's the shortest? If not, ...

There are $N$ men. $K$ of them are knights, $M$ of them are jokers. $N$ is known, $K$ and $M$ are unknown. You know that: $K + M = N$, $K \gt M$, $M \ge 1$, $N$ is odd. Knights always tell the truth, ...

A man is sitting in a dark room. In front of him is a pile of 100 cards. He knows that there are 90 cards faced up and 10 cards faced down. Is it possible for the man to form two piles from these ...

The question of twelve balls and a scale is probably the best-known example of the "find the ball of a different weight" problem. But does it generalize? Is there a general way to find a weighing ...

We are looking for 4 categories. Other (independently solvable) puzzles of this type: 2, 3, 4, 5, 6, 7, 8, 9, 10.

This puzzle is part of the ‘Twelve Labours’ series. Previous instalments can be found here: Prologue | 01 | 02 Hercules was grateful the morning sun wasn’t hotter as he pulled the heavy flatbed ...

Here's an oldie but goodie from The Daily WTF; I paraphrase to avoid copyright issues: A middle school math teacher, who also happened to be the P.E. coach, made the following deal with the non-...

I'm amazed that, although well known, this problem hasn't been posted yet. Monty Hall You are on a game show. The host of the show shows you three doors. He tells you that behind one of them, is a ...

You wake up one morning, and immediately look over at the letter on your bedside table. It reads: Dear [redacted]: You have been chosen to assemble the most powerful thing in the world - the [...

Here are three ways of splitting the letters of the English alphabet into two groups: 1) ABDOPQR; CEFGHIJKLMNSTUVWXYZ 2) BCDGJOPQRSU; AEFHIKLMNTVWXYZ 3) DFHIJLNOPRTUVXYZ; ABCEGKMQSW In each case, ...

This puzzle replaces all numbers with other symbols. Your job, as the title suggests, is to find what number fits in the place of $\bigstar$. All symbols abide to the following rules: Each symbol ...

You've probably heard about challenges with water jugs, so why not try a few? Use 3- and 5- liter jugs to get 4 liters. Use 5- and 7- liter jugs to get 4 liters. This one's different. How many ...

Note: This is a Guide not a Puzzle ciphers are quite common now on puzzling, and at first can seem quite confusing. But ciphers are bigger than this site, used worldwide by companies and secret ...

You are on your way to visit your Grandma, who lives at the end of the valley. It's her birthday, and you want to give her the cakes you've made. Between your house and her house, you have to cross 7 ...

Abraham Van Helsing and Jonathan Harker play a game against Count Dracula. The three players agree on the following rules: Count Dracula and Van Helsing enter the crypt, while Jonathan Harker ...

A group of N pirates has come by a chest containing 200 gold coins. Their rules require that the coins be distributed by the following approach. The pirates are ranked from fiercest to meekest and ...

Here's a fun (albeit difficult) one: Make these equations true using arithmetic operations: ...

At a party last night, my friends Alice and Bob did a magic trick. Any ideas how it worked? Alice shuffled a pack of cards, and asked me to take five. I looked at them. She put the rest of the pack ...

John and Jane are playing a game. They both go to the bank and get 1000 euros in 2 euros. So each of them has 500 euros at stake. They then find a large rectangle table and decide who wins the ...

(This is the community metapuzzle, discussed in this meta thread. It requires answers from nine other puzzles linked below.) You find a mysterious device sitting on the ground. It's labelled in a ...

Let's pack some (one or more) T hexominoes together with some (one or more) small $a\times b$ rectangles into some bigger $m\times n$ rectangle without holes and overlapping pieces. For example, I ...

Each of the puzzles below gives a two-word answer. Solve the puzzles and arrange the resulting 16 words into four groups of four, each with a common theme. The resulting group names form a clue for ...

We are looking for an idiom. Hint 1: Hint 2: Other (independently solvable) puzzles of this type: 1, 2, 3, 4, 5, 6, 8, 9, 10.

Can you determine if it's possible to draw a geometric figure (made up from shapes like rectangles, triangles, and other regular shapes) with one pen stroke and not drawing the same line twice. I am ...

These quaint looking coasters appear to have been thrown haphazardly on the table. However, there is a 10-letter word to be found, which is the answer to this puzzle. Other (independently solvable) ...

You die and ascend to heaven, there is a knight (truth-teller), a knave (pure liar) and a joker (random) sitting on a cloud - they all look the same. In order to gain entry you must determine their ...

Use $2$ $0$ $1 $ and $8$ to make the number $67$ RULES You must use all 4 digits. Only the digits 2, 0, 1, and 8 can be used. You can make multi-digit numbers out of the numbers. Examples: 20, 82, ...

We are looking for the name of a country leader. Other puzzles of this type: 1, 2, 3, 4, 5, 7, 8, 9, 10.

A party is being held at a local mansion. The host is very rich and his success is because of one thing ~ his famous recipe for Spaghetti! The only guests that may attend are people who correctly ...

We are looking for a 3-word phenomenon. Hint 1: Hint 2: Hint 3: Hint 4: Other (independently solvable) puzzles of this type: 1, 2, 3, 4, 5, 6, 7, 8, 10.

This puzzle is part of the ‘Twelve Labours’ series. Previous instalments can be found here: Prologue | 01 | 02 | 03 Now one crate lighter, Hercules made his way back up the road to the Erymanthian ...

This puzzle replaces all numbers with other symbols. Your job, as the title suggests, is to find what number fits in the place of $\bigstar$. All symbols abide to the following rules: Each symbol ...

We are looking for a song (artist and title). Other (independently solvable) puzzles of this type: 1, 3, 4, 5, 6, 7, 8, 9, 10.

We are looking for a 12-letter word. Other (independently solvable) puzzles of this type: 1, 2, 3, 4, 5, 6, 7, 9, 10.

In a Formula 1 race, the chequered flag was waved so violently that the black and white patches got mixed up. Who was waving the flag, when and where? Other (independently solvable) puzzles of this ...

We are looking for 4 countries/kingdoms/sovereign states which do not exist anymore. Hint: Other (independently solvable) puzzles of this type: 1, 2, 4, 5, 6, 7, 8, 9, 10.

This is a Heyacrazy puzzle. Heyacrazy is an original genre, inspired by the "two border" rule of Heyawake and Heyawacky. Rules of Heyacrazy: Shade some cells of the grid. Shaded cells ...

We are looking for a song (artist and title). Other (independently solvable) puzzles of this type: 1, 2, 3, 4, 6, 7, 8, 9, 10.

Dear Puzzling, Remember me? I have some exciting news for you. I'm starting on a new journey to visit a few wonderful landmarks around the world. In case you want to follow my travels, I'll send you a ...

Your partner's space ship has crashed on an uninhabited planet. Only the radio transmitter and his compass were still in operation. He asks you to rescue him, and tells you how to find him by the ...

Look, you don't know me. We've never met. But, like I said, I need you to listen... I had the most disturbing dream the other night... Woke up in a cold sweat and couldn't get back to sleep. It wasn'...

One needs to find the number under the car.

You are in a room with two adjacent doors locked by four sliding bolts. The bolts are movable and block only one door at a time; however, you do not know which bolt currently is blocking which door. ...

When you're looking at a logical word puzzle, what sorts of clues should you try to look for to solve them? There have been quite a few puzzles posted to this site so far that I spent a few minutes ...

You are on a rowboat in the middle of a large, perfectly circular lake. On the perimeter of the lake is a monster who wants to eat you, but fortunately, he can't swim. He can run (along the perimeter)...

Given an 8x8 chessboard, your goal is to "cover" each space on the board with the fewest possible number of pieces. A space is "covered" if there is a piece on it, or if a piece on the board can be ...

This problem is commonly cited as a Microsoft interview problem, although I have paraphrased it here to involve a river and a boat instead of a bridge and a flashlight, and tweaked the crossing times ...

A very short riddle just came to my mind, let's see if it can be cracked: see me once, food can usually be found see me twice, thundering typhoons all around hints are coming daily, if needed. ...

This is a Statue Park puzzle. Rules of Statue Park: Shade some cells of the grid to form the given set of pieces. Pieces may be rotated or reflected. Pieces cannot be orthogonally adjacent (though ...