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Questions tagged [strategy]

A puzzle whose solution is a methodological plan of action for realizing a specific goal.

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72 votes
7 answers
135k views

Twelve balls and a scale

You are given twelve identical-looking balls and a two-sided scale. One of the balls is of a different weight, although you don't know whether it's lighter or heavier. How can you use just three ...
user avatar
102 votes
7 answers
25k views

Why does this solution guarantee that the prince knocks on the right door to find the princess?

I found this puzzle online: On the top floor of a castle lives a princess. The floor has 17 bedrooms arranged in a row. Each bedroom has doors connecting to the adjoining bedrooms as well as to the ...
WendiKidd's user avatar
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46 votes
4 answers
5k views

Which switch goes to which bulb?

You are in a room with three switches, labeled $A$, $B$, and $C$. Initially, each switch is in an off state. In an adjoining room, there are three incandescent light bulbs. Your task is to ...
Xynariz's user avatar
  • 3,620
35 votes
1 answer
9k views

Coins on a table

John and Jane are playing a game. They both go to the bank and each get 1000 euros in two-euro pieces. So each of them has 500 coins at stake. They then find a large rectangle table and decide that ...
Kevin's user avatar
  • 480
53 votes
3 answers
7k views

Sliding Bolt Puzzle

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. ...
diabonas's user avatar
  • 968
34 votes
8 answers
6k views

Dinosaur egg drop

Archeologists discover two dinosaur eggs, and you are given the chance to test the durability of these eggs (bad move on their part). Suppose that these eggs will absorb a specific amount of force ...
Neil's user avatar
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32 votes
4 answers
22k views

Learning to Solve a River Crossing Puzzle

I have seen many variations of the following puzzle: Once upon a time, a farmer went to the market and purchased a fox, a goose, and a bag of beans. On his way home, the farmer came to the bank of ...
Xynariz's user avatar
  • 3,620
16 votes
4 answers
45k views

Is it possible to use one sequence of moves to solve the Rubik's cube from any position?

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, ...
warspyking's user avatar
  • 14.5k
62 votes
5 answers
9k views

How to beat Count Dracula

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 ...
Gamow's user avatar
  • 45.7k
28 votes
3 answers
9k views

The lake monster

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)...
Neil's user avatar
  • 2,116
11 votes
6 answers
16k views

1 Fake Coin among N Amount of coins

You are given $N$ coins which consists of only $1$ fake coin. You also have a sensitive old-fashioned Pan Balance Scale. You are asked to find the fake coin in totally 5 times weighing on the Pan ...
Oray's user avatar
  • 30.4k
21 votes
11 answers
69k views

6 Tries to Guess a Number Between 1-100

After every time you guess, you're told if you're right, too high, or too low. Is there a strategy you can use to guarantee you'll get it on your 6th attempt (or lower)? I know a strategy to get it ...
warspyking's user avatar
  • 14.5k
78 votes
12 answers
15k views

Turn off all lights in a ring-shaped palace

Not a very difficult question, but one I enjoyed nonetheless and wanted to share with the community. You are a servant in a palace. The palace is in the shape of a circle, and you do not know how ...
user avatar
17 votes
3 answers
4k views

Sink the Submarine

There is submarine somewhere on the number line. Initially (say, at midnight), it is at position $A$, and is moving $B$ units per hour to the right, where $A$ and $B$ are both integers; both $A$ and $...
Mike Earnest's user avatar
  • 32.5k
14 votes
2 answers
3k views

10 prisoners and 10 lists of numbers [duplicate]

10 prisoners are held captive by a cruel warden. One day he gathers them in the prison hall and tells them about a new game he wants to play: "Tomorrow, I will assign each one of you a random ...
yotabyte's user avatar
  • 151
11 votes
1 answer
3k views

20 coins on the table

Two boys , Brian and Gabe, decide to play a game. They lay 20 coins on the table. Each player took turns taking 1, 2, or 3 coins. Whoever took the last coin won. Brian thought if he went first, he'd ...
warspyking's user avatar
  • 14.5k
35 votes
12 answers
9k views

The total cost of salaries in a company

Story Version (scroll for TL;DR) It's the end of the first quarter of 2017. This means it's the end of the 2016 fiscal year (at least in my country it is). It's time to draw the line. So the CEO did ...
Marius's user avatar
  • 18.2k
30 votes
6 answers
201k views

Clever ways to solve Mastermind?

Is there any specific way to solve Mastermind? Apart from the first step that is pure chance, is there any way to continue based on the colors that you think are correct?
Shevliaskovic's user avatar
14 votes
7 answers
2k views

Faulty computers

You have $99$ computers in a LAN room, and you know that at least $50$ are working. The others can be faulty. The only thing you are allowed to do is to ask computer $i$ the question "Is computer $j$ ...
Denis's user avatar
  • 759
13 votes
5 answers
4k views

Labeling wires in a bundle

At a remote location, you just finished trenching a data cable across a large plot of land. The cable has 64 individual wires that are not color-coded or labeled. You have a wire stripper, a simple ...
Anon's user avatar
  • 1,179
10 votes
3 answers
2k views

The Expedition Into The Ancient Cave

You are a archeologist and have taken 8 of your students on a expedition trip to a ancient cave to try and find ancient treasure. After you and your team entered the cave, you travel as a group ...
DemonicBirdFlu's user avatar
79 votes
3 answers
6k views

A secret polynomial

Alice has a secret polynomial $P$ with positive integer coefficients. When Bob gives Alice a positive integer $n \neq 2016$, Alice replies with the value of $P(n)$. After doing this several times, Bob ...
rnaylor's user avatar
  • 2,621
52 votes
4 answers
6k views

The lion and the zebras

The lion plays a deadly game against a group of 100 zebras that takes place in the steppe (= an infinite plane). The lion starts in the origin with coordinates $(0,0)$, while the 100 zebras may ...
Gamow's user avatar
  • 45.7k
34 votes
9 answers
6k views

Wolves and sheep

All the sheep were living peacefully in the Land of Shewo. But suddenly they were struck by a danger. A few wolves dressed up as sheep entered the territory of Shewo and started killing the sheep one ...
wanderer's user avatar
  • 1,198
28 votes
7 answers
2k views

23 Clones and Two Lightbulbs

Rise and shine, Mister Bond. James awoke to find himself yet again imprisoned by an evil genius. At least, that's what he presumed. He was alone in a room with a strange device: it consisted of a ...
Mike Earnest's user avatar
  • 32.5k
21 votes
4 answers
1k views

Strategy to beat the casino over the long haul

$A$ and $B$ are attempting to beat the casino again, and the rules are the same: Each round, $A$, $B$, and the casino simultaneously decide to show a $0$ or a $1$. If all three numbers match, $A$ ...
Tyler Seacrest's user avatar
18 votes
1 answer
7k views

What is the strategy to solve Simon Tatham's Twiddle?

Consider the goal 3x3 position: You must reach this position by rotating 2x2 blocks by some multiple of 90 degrees like so: Orientation of each individual number is preserved. What is the ...
greenturtle3141's user avatar
17 votes
9 answers
4k views

Red and Blue in the Chocolate Fountain Room

Where: Hackanoogie Prison. When: Who cares? The Master Key Keeper had had a really good day and in a fit of insanity and niceness decided to let all the inmates to go free if they manage to carry ...
Ben's user avatar
  • 2,617
16 votes
2 answers
2k views

Escaping a hungry lion you can't outrun

You are at the edge of an enormous circular arena. A hungry lion is eying you from the centre of this area. You are both capable of running at the same maximum speed, but constraint within the arena. ...
Johannes's user avatar
  • 4,400
13 votes
2 answers
1k views

How to survive, with statistics

You are kidnapped and your offender plays a game with you. In front of you are 2 boxes, containing a total of 50 white balls and 50 black balls. The kidnapper will pull out a ball from one of the two ...
hetzi's user avatar
  • 305
2 votes
1 answer
419 views

Master and Slave versus Bob: hard version

Continuation of: "Sub-puzzle: Master and Slave versus Bob the Violent but Honest Psychopath" and "Master and Slave versus Bob: easy version" The hard version is identical to the easy version (see ...
deep thought's user avatar
  • 5,168
74 votes
5 answers
8k views

Can the Policeman catch the Thief?

The town of Squareshire has six streets: four sides of a square and the lines joining the midpoints of opposite sides. $\hskip2in$ A policeman is chasing a thief along these streets. If they are ...
Ankoganit's user avatar
  • 19.6k
39 votes
11 answers
77k views

How can one solve a Rubik's cube without relying on guides/algorithms?

I am wondering who is able to solve Rubik's cube just by thinking without knowing the rules behind it. As far as I know the inventor Ernő Rubik was professor of architecture and he intended to help ...
Thomas's user avatar
  • 515
38 votes
5 answers
2k views

Strategy to beat the Casino

Two players, $A$ and $B$, and the Casino play a game. It involves showing zeros or ones: each player picks $0/1$ and also the Casino picks $0/1$. If the Casino and both players $A$ and $B$ show the ...
Quara's user avatar
  • 419
34 votes
3 answers
3k views

There are at least three Kevins on Puzzling. I plan to trap them in my labyrinth

Note: please do not edit the title! It originates in a challenge in Stack Overflow chat. I have rounded up all ten (currently) of the Puzzling SE users named Kevin and trapped them in my labyrinth. ...
Rand al'Thor's user avatar
33 votes
4 answers
3k views

The Devil's Brother

The 1933 movie "The Devil's Brother" (also known under the title "Fra Diavolo") takes place in the Northern Italy of the early 18th century. Stan Laurel and Oliver Hardy play the fierce robbers ...
Gamow's user avatar
  • 45.7k
19 votes
8 answers
2k views

30 fake coins out of 99 coins

You are given 99 coins which consists of 30 fake ones. You also have a digital balance scale with perfect precision that shows how much difference between weighs you put on. For example, if you put 10 ...
Oray's user avatar
  • 30.4k
19 votes
3 answers
1k views

Reunite the Stars

On an infinite plane, the Prime Star has disintegrated into four constituent stars, the North Star, the South Star, the East Star and the West Star, each traveling at a constant speed of 1 in their ...
Eric's user avatar
  • 6,536
16 votes
4 answers
6k views

The Mexican Standoff

There are three cowboys in a Mexican standoff against each other, named Juan, José, and Jorge. Juan is the straightest shooter in the West, and can hit his target 100% of the time. José, who has a ...
user avatar
14 votes
3 answers
725 views

Strategy to beat the Casino reversed

Let's consider Strategy to beat the Casino puzzle, but reverse it - fix number of losses and ask a question about amount of rounds: Two players, A and B, and the Casino play a game. The game consists ...
klm123's user avatar
  • 16.3k
9 votes
1 answer
2k views

99 chips into more chips

You are at a casino in Vegas and you have earned 99 chips by playing poker! While you are checking out a slot machine, someone comes to you and congratulates you that you have a chance to make more ...
Oray's user avatar
  • 30.4k
7 votes
3 answers
915 views

Dinosaur Egg Drop v2

This question is a little different and kinda follow-up version of Dinosaur Egg Drop 1- You have 100 story building and 6 Apatosaurus dinosaur eggs. 2- You have 81 story building and 3 ...
Oray's user avatar
  • 30.4k
2 votes
1 answer
300 views

Master and Slave versus Bob: easy version

Continuation of: "Sub-puzzle: Master and Slave versus Bob the Violent but Honest Psychopath" Continued in: "Master and Slave versus Bob: hard version" Previously I described a game that is played ...
deep thought's user avatar
  • 5,168
0 votes
3 answers
541 views

Sub-puzzle: Master and Slave versus Bob the Violent but Honest Psychopath

[I created this as a sub-puzzle to "Strategy to beat the Casino reversed", that has been sitting unsolved for months. You may wish to read that puzzle first, but this is self-contained. My answer to ...
deep thought's user avatar
  • 5,168
93 votes
9 answers
14k views

Coin Flipping Game with the Devil

You die, and awake in Hell. Satan awaits you, and has prepared a curious game. He has arranged $n$ quarters in a line, going in the east/west direction. He placed the coins at the ends tails up, and ...
Mike Earnest's user avatar
  • 32.5k
62 votes
3 answers
7k views

Left coin, right coin, last coin?

In this game, all players start sitting at a round table, each with a coin in their hand. At every turn, all players toss their coins together and put them on the table in front of them. Then each ...
GOTO 0's user avatar
  • 13.5k
57 votes
7 answers
10k views

The Circular Prison of Unknown Size

You are the president of a secret society of mathematicians with $n$ members, including yourself. No one in the society knows what $n$ is. The dictator of the world, in an effort to erase mathematics ...
Mike Earnest's user avatar
  • 32.5k
47 votes
2 answers
2k views

lolcatz can haz ur infinit cheeseboard

This is a problem on an infinite chessboard with pieces called lolcatz. They can move like queens or knightriders, but have a strange disadvantage... ... you've never heard of knightriders? Well, ...
deep thought's user avatar
  • 5,168
40 votes
5 answers
15k views

Duel between the knight and the dragon

A dragon and a knight live on an island where the only sources of fresh water are a pond (containing ordinary water) and six wells, numbered 1 to 6. Each well's water is completely indistinguishable ...
Neil's user avatar
  • 2,116
34 votes
9 answers
5k views

Two Sheriffs and Eavesdroppers

Two sheriffs are working on a case to find one culprit. There were initially 8 suspects; through independent work, each sheriff has narrowed this down to a list of 2. Because they are good sheriffs, ...
Mike Earnest's user avatar
  • 32.5k