Practice Problems

Master the art of lateral thinking with 105 curated riddles.

Riddle #1
MEDIUM

The Bridge at Midnight

GoogleAmazonLogic
Riddle #2
EASY

Burning Ropes of Time

MicrosoftMathLateral Thinking
Riddle #3
EASY

The Three Light Switches

GoogleAdobeLateral Thinking
Riddle #4
MEDIUM

Heavy Gold Gold coins

AmazonMathLogic
Riddle #5
EASY

The Lily Pad Exponential Pond

MetaMathPattern Recognition
Riddle #6
MEDIUM

The Monty Hall Dilemma

MetaLogicMath
Riddle #7
MEDIUM

Measuring Water with Pitchers

AmazonMathLogic
Riddle #8
HARD

The Poisoned Wine Bottles

GoogleMathLogic
Riddle #9
MEDIUM

The Two Sand Hourglasses

AdobeLogicLateral Thinking
Riddle #10
HARD

The Infinite Hallway of Lockers

MicrosoftMathPattern Recognition
Riddle #11
EASY

Ferrying Animals Across the River

MetaLogicLateral Thinking
Riddle #12
HARD

Estimating Piano Tuners in Chicago

GoogleEstimationLogic
Riddle #13
HARD

The Outbreak of Blue Eyes

MetaLogicLateral Thinking
Riddle #14
MEDIUM

The Burning Desert Crossing

AmazonLogicEstimation
Riddle #15
EASY

The Patterns in the Sequence

AdobePattern RecognitionMath
Riddle #16
HARD

The Fragile Floors

GoogleAmazonOptimizationLogic
Riddle #17
HARD

Rivals on a Raft

MicrosoftMetaGame TheoryLogic
Riddle #18
EASY

The Odd Ball Out

AppleAdobeOptimizationLogic
Riddle #19
HARD

The Infinite Staircase

GoogleNetflixMathInfinity
Riddle #20
MEDIUM

Glasses in the Dark

AppleAmazonGame TheoryLogic
Riddle #21
HARD

The Marked Coin

MicrosoftAdobeOptimizationLogic
Riddle #22
HARD

The Surprise Verdict

GoogleMicrosoftParadoxesPhilosophy
Riddle #23
HARD

The Number-Matching Escape

GoogleNetflixProbabilityCombinatorics
Riddle #24
HARD

The Twin Envelopes

AmazonMetaParadoxesProbability
Riddle #25
MEDIUM

The Hotel That Never Fills Up

AppleGoogleInfinityPhilosophy
Riddle #26
HARD

The Waking Uncertainty

MetaMicrosoftProbabilityPhilosophy
Riddle #27
EASY

The Vanishing Dollar

AdobeAppleLogicMath
Riddle #28
HARD

The Survivor's Position

GoogleAdobeCombinatoricsLogic
Riddle #29
MEDIUM

The Desert Stockpile

AmazonMicrosoftOptimizationLogic
Riddle #30
MEDIUM

The Marble Jar Gamble

GoogleAmazonProbabilityGame Theory
Riddle #31
EASY

The Locked Safe Code

MicrosoftAdobeLogicLogic Grids
Riddle #32
MEDIUM

The Truthful and the Deceptive

MetaAppleLogicPhilosophy
Riddle #33
HARD

The Sinking Probability

GoogleNetflixProbabilityStatistics
Riddle #34
MEDIUM

The Duplicate Birthday

AmazonMetaProbabilityStatistics
Riddle #35
HARD

The Cheating Coin

GoogleMicrosoftProbabilityStatistics
Riddle #36
EASY

The Crowded Elevator

AmazonAdobeProbabilityCombinatorics
Riddle #37
MEDIUM

The Recursive Staircase

AppleNetflixDynamic ProgrammingCombinatorics
Riddle #38
EASY

The Sock Drawer

AmazonMicrosoftPigeonholeLogic
Riddle #39
EASY

The Handshake Count

GoogleMetaCombinatoricsLogic
Riddle #40
EASY

The Stuck Clock

AppleAdobePattern RecognitionLogic
Riddle #41
EASY

The Coin on the Table

GoogleNetflixGame TheoryGeometry
Riddle #42
MEDIUM

The Painted Cube

AmazonMetaGeometryProbability
Riddle #43
MEDIUM

The Liars at the Round Table

MicrosoftAppleGame TheoryConstraints
Riddle #44
MEDIUM

The Number on My Forehead

GoogleAdobePattern RecognitionConstraints
Riddle #45
EASY

The Weight of Words

AmazonGooglePattern RecognitionLogic
Riddle #46
MEDIUM

The Relay Race Order

MicrosoftAdobeConstraintsLogic
Riddle #47
MEDIUM

The Train Tunnel Escape

MetaNetflixGeometryLogic
Riddle #48
EASY

The Night Watchman's Dilemma

ScenarioLogicDeductionPhysics
Riddle #49
EASY

The Tea Estate Mystery

ScenarioLogicDeductionGame Theory
Riddle #50
EASY

The Lighthouse Keeper's Bottles

ScenarioLogicDeductionOptimization
Riddle #51
MEDIUM

The Cartographer's Code

ScenarioNumber TheoryDeductionLogic
Riddle #52
MEDIUM

The Mango Orchard Division

ScenarioGeometryCombinatoricsLogic
Riddle #53
MEDIUM

The Spice Merchant's Weights

ScenarioNumber TheoryLogicDeduction
Riddle #54
EASY

The Password on the Sticky Note

ScenarioNumber TheoryDeductionLogic
Riddle #55
EASY

The Antique Clock Shop

ScenarioNumber TheoryLogicPattern Recognition
Riddle #56
MEDIUM

The Landlord's Garden

ScenarioGeometryLogicMath
Riddle #57
HARD

The Diamond Vault

ScenarioNumber TheoryLogicDeduction
Riddle #58
MEDIUM

The River Island Census

ScenarioNumber TheoryModular ArithmeticCRT
Riddle #59
MEDIUM

The Chess Tournament Bracket

ScenarioCombinatoricsLogicPattern Recognition
Riddle #60
HARD

The Sandstone Smuggler

ScenarioNumber TheoryLogicDeduction
Riddle #61
HARD

The Inheritance Grid

ScenarioMagic SquaresCombinatoricsLogic
Riddle #62
MEDIUM

The Astronomer's Telescope

ScenarioSequencesNumber TheoryPattern Recognition
Riddle #63
MEDIUM

The Trapped Miners

ScenarioGame TheoryOptimizationLogic
Riddle #64
HARD

The Stolen Sapphire

ScenarioNumber TheoryModular ArithmeticDeduction
Riddle #65
MEDIUM

The Pension Fund Puzzle

ScenarioNumber TheorySequencesMath
Riddle #66
HARD

The Codebreaker's Grid

ScenarioMagic SquaresCombinatoricsLogic
Riddle #67
MEDIUM

The Colour-Blind Painter

GoogleAmazonCombinatoricsGraph Theory
Riddle #68
MEDIUM

The Cracked Safe Combination

MicrosoftAdobeNumber TheoryLogic
Riddle #69
MEDIUM

The Bacteria Colony

AppleMetaExponential GrowthLogic
Riddle #70
HARD

The Unfair Coin Tournament

GoogleNetflixProbabilityGame Theory
Riddle #71
MEDIUM

The Locked Library

AmazonMetaCombinatoricsPermutations
Riddle #72
MEDIUM

The Toll Road Dilemma

GoogleMicrosoftGraph TheoryOptimization
Riddle #73
MEDIUM

The Chessboard Squares

AppleAdobeCombinatoricsMath
Riddle #74
HARD

The Forgetful Professor

GoogleNetflixProbabilityDerangements
Riddle #75
MEDIUM

The Password Guessing Game

AmazonMicrosoftGame TheoryLogic
Riddle #76
HARD

The Dividing Necklace

MetaAdobeCombinatoricsModular Arithmetic
Riddle #77
MEDIUM

The Landlord and the Tenants

GoogleAmazonCombinatoricsLogic
Riddle #78
HARD

The Negotiator's Dilemma

MicrosoftAdobeGame TheoryLogic
Riddle #79
MEDIUM

The Circuit Board Test

AppleMetaProbabilityOptimization
Riddle #80
MEDIUM

The Folded Paper Tower

GoogleNetflixExponential GrowthMath
Riddle #81
HARD

The Four-Digit Lockbox

AmazonMetaBFSLogic
Riddle #82
MEDIUM

The Lazy Librarian's Stack

GoogleMicrosoftInvariantsLogic
Riddle #83
HARD

The Infinite Hotel Upgrade

AppleAdobeInfinityMath
Riddle #84
MEDIUM

The Ant on a Cube

GoogleNetflixGeometryMath
Riddle #85
HARD

The Riddled Auction

AmazonMicrosoftAuctionsGame Theory
Riddle #86
MEDIUM

The Recursive Chocolate Bar

MetaAdobeInvariantsCombinatorics
Riddle #87
EASY

The Extra Rope Around the Earth

GoogleMicrosoftGeometryMath
Riddle #88
EASY

The Probability of Two Strangers Sharing a Birthday

AmazonMetaProbabilityParadox
Riddle #89
HARD

The Surprising Sum of All Natural Numbers

GoogleAdobeSequencesZeta Function
Riddle #90
MEDIUM

The Hotel With Infinite Rooms — All Full, Always Accommodating

MicrosoftAppleInfinityParadox
Riddle #91
MEDIUM

The Unreachable Destination — Zeno's Dichotomy

MetaNetflixLimitsZeno
Riddle #92
MEDIUM

The Probability That Two Numbers Are Coprime

GoogleAmazonProbabilityNumber Theory
Riddle #93
MEDIUM

The Monty Hall Remix — Three Prisoners

AppleNetflixProbabilityMonty Hall
Riddle #94
EASY

The Spinning Coin and the Moving Bee

MicrosoftAdobeSequencesLimits
Riddle #95
HARD

The Unexpected Diagonal — Cantor's Proof

GoogleMetaInfinityCantor
Riddle #96
MEDIUM

The Coastline That Has No Length

AmazonAppleFractalsGeometry
Riddle #97
EASY

The Wheat and the Chessboard

GoogleAmazonExponential GrowthMath
Riddle #98
HARD

The Coin Flip and the Gambler's Ruin

MicrosoftAppleProbabilityGame Theory
Riddle #99
MEDIUM

The Drunkard's Walk Home

MetaNetflixProbabilityLimits
Riddle #100
MEDIUM

The Three-Door Problem Nobody Gets Right

GoogleNetflixProbabilityMonty Hall
Riddle #101
HARD

The Impossible Crossing — Four Switches, One Bulb

AmazonMetaCryptographyXOR
Riddle #102
MEDIUM

The Simpson's Paradox Election

MicrosoftAdobeParadoxStatistics
Riddle #103
HARD

The Pigeons in the Boxes — Infinite Ramsey

GoogleAppleCombinatoricsLogic
Riddle #104
MEDIUM

The Speed of Information — Can You Beat Light?

MetaAdobePhysicsQuantum
Riddle #105
EASY

The Last Digit of 7 to the Power of 7777

AmazonMicrosoftNumber TheoryCryptography