A **brain teaser** is a form of puzzle that requires thought to solve. It often requires thinking in unconventional ways with given constraints in mind; sometimes it also involves lateral thinking. Logic puzzles and riddles are specific types of brain teasers.

One of the earliest known brain teaser enthusiasts was the Greek mathematician Archimedes.^{[1]} He devised mathematical problems for his contemporaries to solve.

- Q:
*If three hens lay three eggs in three days, how many eggs does a (statistical) hen lay in one day?* - A1:
*One third.*(Note: 3 hens = 3 eggs / 3 days → 3 hens = (3 / 3) (eggs / days) → 1 hen = (1 / 3) (egg / days)) - A2:
*Zero or one*(it's hard to lay a third of an egg).

One can argue about the answers of many brain teasers; in the given example with hens, one might claim that all the eggs in the question were laid in the first day, so the answer would be three.

- Q:
*Mary's father has five daughters: 1. Nana, 2. Nene, 3. Nini, 4. Nono. What is the name of the fifth daughter?* - A:
*Mary. The first four daughters all have names with the first 4 vowels, so if someone does not think about the question, they may say the name with the fifth vowel, Nunu. The answer was given at the beginning of the question (ie,***Mary's father**has five...)

- Q:
*What appears once in a minute, twice in a moment, but never in a thousand years?* - A: The letter "M".

- Q:
*I am the beginning of the end, the beginning of eternity, and the end of all time?* - A: The letter "E".

The difficulty of many brain teasers relies on a certain degree of fallacy in human intuitiveness. This is most common in brain teasers relating to conditional probability, because the causal human mind tends to consider absolute probability instead. As a result, controversial discussions emerge from such problems, the most famous probably being the Monty Hall problem. Another (simpler) example of such a brain teaser is the Boy or Girl paradox.

**^**Editors of Time-Life books, Inc. (1989).*The Puzzle Master*. Alexandria, Virginia, USA: Time-Life Books. p. 18. ISBN 0-8097-0928-7.CS1 maint: extra text: authors list (link)

*Brain Teasers*at Curlie – An active listing of links to brain teasers.- Kador, John (2004)
*How to Ace the Brainteaser Interview*. McGraw Hill Professional, ISBN 978-0071440011

For the type of puzzle, see Brain teaserBrainTeaser was a British game show based on the original Dutch format of Puzzeltijd (English: Puzzle Time), first broadcast in 2002 produced by Endemol UK subsidiary Cheetah Productions.

The show was broadcast live, with phone-in viewer puzzles being announced and played during the show in addition to the studio game. During its run until 7 March 2007, it aired on Channel 5 Mondays to Fridays, usually for an hour around lunchtime, with Alex Lovell as the main presenter. Until the end of 2005, Lovell rotated presenting duties on a weekly basis with Craig Stevens, Rachel Pierman and Jonny Gould, at different times in the show's history.

Channel 5 suspended the programme on 8 March 2007 after it was revealed that the production company, Cheetah Productions, had misled viewers regarding winners of the viewer puzzles (which were entered using a premium rate phone number). Actions included publishing fictional names and presenting a member of the production team as a 'winner'. On 26 June 2007, Channel 5 announced that the show had been cancelled after 1122 episodes after media regulator Ofcom fined the channel £300,000.

BrainteaserBrainteaser or brain teaser may refer to:

Brain teaser, a puzzle that requires thought to solve, often requiring thinking in unconventional ways with given constraints in mind

BrainTeaser, a British television game show originally broadcast 2002–2007

Captain Peralta (Brooklyn Nine-Nine)"Captain Peralta" is the eighteenth episode of the second season of the American television police sitcom series Brooklyn Nine-Nine. It is the 40th overall episode of the series and is written by series co-creator Dan Goor and directed by Eric Appel. It aired on Fox in the United States on March 8, 2015.

The show revolves around the fictitious 99th precinct of the New York Police Department in Brooklyn and the officers and detectives that work in the precinct. In the episode, Jake's father comes to visit him but his visit turns out to be a call for helping him into cleaning a drugs charge he received in Canada. Meanwhile, Holt gives the precinct a brain-teaser that he can't even solve.

The episode was seen by an estimated 3.11 million household viewers and gained a 1.5/4 ratings share among adults aged 18–49, according to Nielsen Media Research. The episode received very positive reviews from critics, who praised the Samberg's and Whitford's performance in the episode.

GNOME Games CollectionGNOME Games is a collection of about 15 puzzle video games that is part of the standard free and open-source GNOME desktop environment. They have the look and feel of the GNOME desktop, but can be used without it.

Gary GruberGary R. Gruber (born Brooklyn, New York City, New York) is an American theoretical physicist, educator, and author who has written many books and software programs for standardized test preparation.

His work focuses on test-taking and critical thinking skills and claims sales of more than 7 million books. His writings include the Gruber's Complete Guide series as well as books and columns of brain teaser puzzles and other articles.

He also works with schools, school districts, state departments of education and other educational organizations in the development of testing and critical thinking skills and educational motivation programs.

Gbrainygbrainy is a brain teaser game for GNOME designed for use in education. It is licensed under the GNU GPL. The game was written in C# and has since been ported to the Sugar graphical environment, to Microsoft Windows.

Specifically, it contains the following:

Logic puzzles - games designed to challenge reasoning and thinking skills

Mental calculation - games based on arithmetical operations designed to improve mental calculation skills

Memory trainers - games designed to challenge short term memory

Verbal analogies - games that challenge your verbal aptitude

Hoot N HollerHoot N Holler is a steel family roller coaster at Six Flags Darien Lake in New York. It is manufactured by Zierer.

IdiotestIdiotest (a portmanteau of "idiot" and "test" and stylized with the second letter i inverted) is an American television game show broadcast by Game Show Network (GSN). Hosted by Ben Gleib, the series features contestants in teams of two competing to answer brain teaser and puzzle questions. The winning team advances to a bonus round for an opportunity to increase their winnings to $10,000. The series was announced at GSN's upfront presentation in March 2014, and the first episode premiered on August 12 of that year. In December 2018, the first season became available to watch on Netflix.Critical reception for the series has been mixed, with one writer calling it "enjoyable" while another called it "uninteresting." Additionally, GSN released an online game midway through the first season that allows users to answer questions from the series' past episodes.

Lisa the Simpson"Lisa the Simpson" is the seventeenth episode of The Simpsons' ninth season. It originally aired on the Fox network in the United States on March 8, 1998. In the episode, Lisa fears that she may be genetically predisposed to lose her intelligence after Grandpa tells her of a family gene that can permanently take away intelligence.

"Lisa the Simpson" was written by Ned Goldreyer and directed by Susie Dietter. This episode was the final episode with Bill Oakley and Josh Weinstein as show runners. It received generally positive reviews from critics, and is considered one of the best episodes of the ninth season.

List of impossible puzzlesThis is a list of puzzles that cannot be solved.

15 puzzle – Slide fifteen numbered tiles into numerical order. Impossible for half of the starting positions.

Five room puzzle – Cross each wall of a diagram exactly once with a continuous line.

MU puzzle – Transform the string MI to MU according to a set of rules.

Mutilated chessboard problem – Place 31 dominoes of size 2×1 on a chessboard with two opposite corners removed.

Coloring the edges of the Petersen graph with three colors

Seven Bridges of Königsberg – Walk through a city while crossing seven bridges exactly once.

Three cups problem – Turn three cups right-side up after starting with one wrong and turning two at a time.

Three utilities problem – Connect three cottages to gas, water, and electricity without crossing lines.

The carousel problem – Create a carousel that is capable of 11/11 key features. Currently only 9/11 is believed to be possible

List of puzzle topicsThis is a list of puzzle topics, by Wikipedia page.

Acrostic

Anagram

Back from the klondike

Ball-in-a-maze puzzle

Brain teaser

Burr puzzle

Chess problem

Chess puzzle

Computer puzzle game

Cross Sums

Crossword puzzle

Cryptic crossword

Cryptogram

Daughter in the box

Disentanglement puzzle

Edge-matching puzzle

Egg of Columbus

Eight queens puzzle

Einstein's Puzzle

Eternity puzzle

Fifteen puzzle

Fox, goose and bag of beans puzzle

Geomagic square

Globe puzzle

Graeco-Latin square

Gry

Happy Cube

Insight

Jigsaw puzzle

KenKen

Knights and knaves

Knight's Tour

Lateral thinking

Latin square

Letter bank

Lock puzzle

Logic puzzle

Logo extraction puzzle

Magic square

Mahjong solitaire

Matchstick puzzle

Mathematical puzzle

Maze

Mechanical puzzle

Merkle's Puzzles

Minus Cube

Morpion solitaire

N-puzzle

National Puzzlers' League

Nikoli

Nob Yoshigahara Puzzle Design Competition

Nurikabe

Packing problem

Paint by numbers

Peg solitaire

Pentomino

Pirate loot problem

Plate-and-ring puzzle

Prisoners and hats puzzle

Problem solving

Rattle puzzle

Rebus

Rubik's Cube

Speedcubing

Pocket Cube

Rubik's Magic

Rubik's Revenge

Situation puzzle

Sliding puzzle

Snake cube

Sokoban

Soma cube

Stick puzzle

Sudoku

Tangram

Thinking outside the box

Three-cottage problem

Three cups problem

Tiling puzzle

Tour puzzle

Tower of Hanoi

T puzzle

Tsumego

Tsumeshogi

Verbal arithmetic

WOWCube

Wire puzzle

Wire-and-string puzzle

XYZZY Award for Best Individual Puzzle

Lock puzzleA lock puzzle is a type of mechanical puzzle. It consists of a lock with unusual or hidden mechanics. Such locks are sometimes called trick locks, because there is a trick to opening them which needs to be found. A key is usually needed and it is sometimes a part of the trick mechanism but there exist trick locks with no keys as well.

Lock puzzles have a long history.

Logic puzzleA logic puzzle is a puzzle deriving from the mathematics field of deduction.

Monty Hall problemThe Monty Hall problem is a brain teaser, in the form of a probability puzzle, loosely based on the American television game show Let's Make a Deal and named after its original host, Monty Hall. The problem was originally posed (and solved) in a letter by Steve Selvin to the American Statistician in 1975 (Selvin 1975a), (Selvin 1975b). It became famous as a question from a reader's letter quoted in Marilyn vos Savant's "Ask Marilyn" column in Parade magazine in 1990 (vos Savant 1990a):

Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice?

Vos Savant's response was that the contestant should switch to the other door (vos Savant 1990a). Under the standard assumptions, contestants who switch have a 2/3 chance of winning the car, while contestants who stick to their initial choice have only a 1/3 chance.

The given probabilities depend on specific assumptions about how the host and contestant choose their doors. A key insight is that, under these standard conditions, there is more information about doors 2 and 3 that was not available at the beginning of the game, when door 1 was chosen by the player: the host's deliberate action adds value to the door he did not choose to eliminate, but not to the one chosen by the contestant originally. Another insight is that switching doors is a different action than choosing between the two remaining doors at random, as the first action uses the previous information and the latter does not. Other possible behaviors than the one described can reveal different additional information, or none at all, and yield different probabilities. Yet another insight is that your chance of winning by switching doors is directly related to your chance of choosing the winning door in the first place: if you choose the correct door on your first try, then switching loses; if you choose a wrong door on your first try, then switching wins; your chance of choosing the correct door on your first try is 1/3, and the chance of choosing a wrong door is 2/3.

Many readers of vos Savant's column refused to believe switching is beneficial despite her explanation. After the problem appeared in Parade, approximately 10,000 readers, including nearly 1,000 with PhDs, wrote to the magazine, most of them claiming vos Savant was wrong (Tierney 1991). Even when given explanations, simulations, and formal mathematical proofs, many people still do not accept that switching is the best strategy (vos Savant 1991a). Paul Erdős, one of the most prolific mathematicians in history, remained unconvinced until he was shown a computer simulation demonstrating the predicted result (Vazsonyi 1999).

The problem is a paradox of the veridical type, because the correct choice (that one should switch doors) is so counterintuitive it can seem absurd, but is nevertheless demonstrably true. The Monty Hall problem is mathematically closely related to the earlier Three Prisoners problem and to the much older Bertrand's box paradox.

QuickSpotQuickSpot (右脳の達人 爽解！まちがいミュージアム, Unou no Tatsujin: Soukai! Machigai Museum) is a video game for the Nintendo DS developed by Namco Bandai. It is designed similar to games such as Brain Age which uses simple brain teaser to exercise reflexes and brain function. It is a part of Nintendo's Touch! Generations brand and is the first in the Uno no Tatsujin series.

Stick puzzleStick puzzles use sets of 'polysticks' (essentially one-dimensional objects) which have to be assembled into two- or three-dimensional configurations.

Polysticks are configurations of joined or unjoined thin (ideally one-dimensional) 'sticks'. The sticks may be matchsticks, or pieces of straw, wire or similar.

A special (and very old) class of stick puzzles are 'matchstick puzzles', where all parts used are sticks (usually matchsticks) rather than polysticks. Some (trick-)puzzles can only be solved when one assumes that the sticks actually have measurements in more than one dimension.

TeaserTeaser:

One who teases

Cold open, a segment at the beginning of a television program or film before the opening credits

Teaser campaign, an advertising method (including theatrical trailers)

Teaser (animal), a male livestock animal (typically a bull) whose penis has been amputated

Tiling puzzleTiling puzzles are puzzles involving two-dimensional packing problems in which a number of flat shapes have to be assembled into a larger given shape without overlaps (and often without gaps). Some tiling puzzles ask you to dissect a given shape first and then rearrange the pieces into another shape. Other tiling puzzles ask you to dissect a given shape while fulfilling certain conditions. The two latter types of tiling puzzles are also called dissection puzzles.

Tiling puzzles may be made from wood, metal, cardboard, plastic or any other sheet-material. Many tiling puzzles are now available as computer games.

Tiling puzzles have a long history. Some of the oldest and most famous are jigsaw puzzles and the Tangram puzzle.

Other examples of tiling puzzles include:

Conway puzzle

Domino tiling, of which the mutilated chessboard problem is one example

Eternity puzzle

Geometric magic square

Puzz-3D

Squaring the square

Tantrix

T puzzle

PentominoesMany three-dimensional mechanical puzzles can be regarded as three-dimensional tiling puzzles.

Tom GodwinTom Godwin (June 6, 1915 – August 31, 1980) was an American Science Fiction author. Godwin published three novels and twenty seven short stories. His hard SF short story "The Cold Equations" is a notable example of the mid-1950s Science Fiction genre.

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