Recreational Challenges   Alarm Clock Anomaly  When plug-and-play won't play. Birthday Bet   Winning a wager: It helps to know something that the loser does not know. Chase Me, Catch Me Taking painful realities in stride. Counter-Intuitive Cork  A puzzle from childhood that stumps adults. Cross-Number Puzzle   First of its kind, probably for a good reason. Drawbridge Dilemma  Exercise in consensus and ethics, assumptions and suppositions.  Droodle Generation   Simple sketches -- simple, once they are explained. Erg and Ugh   All play and no work defining units and energies. Fuzzy Dice   Dating one decorative talisman -- and yourself. Genesis Won One  An instrument of modesty in art laid bare.  Literary Larvae   Devouring pages while counting them. Magnanimous Month   Celebrating paydays and weekends with numbers. Missing Letters   Finding features in common without seeing them. Mythical Muses   Since they are not real, there is no limit on their numbers. Train Speed   A puzzle from childhood that stumps adults.  Logic and Reasonings Alphabet Group   Never have so many attributes belonged to so few. Balls in Boxes   Sometimes it helps to draw a map of alternatives. Battle of the Buns  It may be OK not to make the pegs fit the holes.  Benford's Law   Something for taxpayers to know to avoid audits. Bottle Royal   Elementary exercise for a long, rainy weekend.. Bucketing Bandwidth   Metaphor for managing a misleading metaphor. Challengee vs Challenger   Winning wager tempting to make/take -- or not. Circling: Ground and Sky   Faster in one way but slower in another. Conservation of Bits   Code compression will never go out of style. Count the Squares  Challenge for children in French and English. Dérailleur de Rigueur   Modern bicycle designs may have gone too far. Fibonacci Fantasy  Where parallel lines meet, so too do the rational and the irrational. Golden Section  Carried away by specious correlations. Gold on the Wing   A juvenile puzzle that stumps adolescents. Hand Over Hand  A real paradox -- well, maybe not. Inches per What?  Share of mind owned by outdated technology.  Jump in a Lake  You can drown in a lake but only if the lake is deep enough. King for a Day  An empire full of next-number puzzles. Least Significant Digits  Listening for a dog not barking.  Materix  The statistics of romantic relationships. Matches These matches are safe for children to play with. Measuring the Moon  Gauging the size of one particular faraway object. MY Missile  Relic of a Cold War stratagem with practical applications. Next Number  Making the most of what is given by making assumptions. Odd Ball Using a balance scale without calibrated weights. Paradox Lost  Where parallel lines meet, so too do the infinite and the infinitesimal. Polarity Happens  An adolescent puzzle that stumps adults. Reversible Ages  Birthday greeting discloses numerical limits. Romance in Numbers  Looking back with nostalgia to pre-positional notation. Scale Steps  Discovery of a new classification for musical instruments. Secret Message  High school puzzle that can stump an undergraduate. Skateboard Mystery  At the end of a jump, where does all the kinetic energy go? Space-Time Singularity  Bizarre combination of location an time. Twelve-Tone Melodies  Making music with mathematical minimalism. Word Problems  Turning a homework dread on its head. Math and Models World Superlatives Collection World's Fastest Airliner World's Fastest Car World's Fastest Dragster World's Largest Machines World's Fastest Train Band Around the Earth  Junior college puzzle that stumps university graduates. Carbon Footprint  Getting carried away with electrical options. Circloid  Discovery of a valid hypothesis and another that is not valid. Claim Game A bimodal distribution offers a complaint-free service. Density Lock A counter-intuitive proposal to prevent traffic jams. Differationale Which solution is right and which solution is wrong. Double Integrity  Numerical mischief in defining the undefined. Easy as Pi  Approximating irrational numbers with rational numbers. Factorial Factoids  Looking for a missing most significant digit. Five Axles Axle loading does not explain highway damage (prequel to Unsprung Secrets) Historic Car Crash  Time of maximum crush-in volume seems to be a constant.  Linear Linkage  Headlined uniqueness in the past found not to be unique. Fermat's Really Last Theorem  Power of foozling for making mathematical history. Look-at-Me Car  Form ever follows function, and function takes energy. Magique Nombre All roads lead to the same number.  But why? Missing Numbers Finding boundless quantities of solutions. Nail-Biter Ballots  Most practical technology for voting is two centuries old. Natural Hypoteneese  What Pythagoras of Samos might do with a spreadsheet. Next Superbowl    Selecting your winning square in the office football pool. Paranormal Numbers    Algebra teacher with psychic powers -- or so it seems. Phantom Circuit    Exploiting a variable that does not vary with dimension. Price of a Point    Rationalizing football's idiosyncratic scoring system. Prime Numbers are Odd   Attributes of the purest of integers.  Psychic Math    Unraveling the secrets of sorcery.  Radicand  Solution to one puzzle calls for new puzzles. Randomly Wrong   Challenges for human-derived randomness. Rational Growth  How to approximate an exponential function with a ratio. Rational Roots   Where parallel lines meet, so too do the infinite and the infinitesimal. Reaman Numeral    Reconstructing a singular mid-Twentieth Century discovery. Reaman Numerals Plural   Dancing with the do-si-do digits. Recursive Sentence   Real gambling payoff for real gamblers. Repeating Decimal Decimals    Producing proper rational fractions. Revenge of the DAR    Central tendency: mean and median do not always meet. Rond-Point  Vehicular flow in a signal-free intersection Roulette's Frets   Mathematical induction for the derivation of 'totorial'.   Short Cut?   Absence of information makes the solution more interesting. Steamboat Hill   Applying conservation retrospectively to one venerable technology. Strange Series   Mountains and foothills in one numerical algorithm. Tin-Can Mystery  Environmental reality: Holes pick the pegs not vice versa. Tip of the Ice Cube   Melting metaphor: floating on oceans vs resting on land. To Brake or Not to Brake   Analyzing the power in coasting. Unsprung Secrets  Proposed explanation for highway damage (sequel to Five Axles). What the Wild Goose Knows   Nature teaches us embarrassing things about us. World's Fastest Car  Analysis of the Bloodhound LSR. World's Fastest Dragster   Being first means getting there first, not speed. World's Largest Machines Arguably the world's most obvious question. Yaw of Averages   Exploring a paradox in central tendencies. Reasoning Meets the Rails Confusion-Free Codes   Not to be confused with comma-free codes. Express vs Local   Getting more there trumps getting there faster. Fast Track   Analyzing the speed penalty of not going straight. Pantograph Design  Making improvements in an aerodynamic eyesore. Single Tracking  Operations versus capital costs in railroad emergencies. Station Stop  Understanding the true through-put limits in railway transit. Streetcar Mystery  Surprising realities in converging and diverging. Trail Braking   Finding the optimum speed for maximizing through-put. Trip Time  Figuring out the impact of having to serve passengers.  World's Fastest Train   Tractive effort taxed by aerodynamic limits. Puzzles in the Skies  Ameliana Collection  1. The Clock Won't Wait  2. Here Comes the Sun  3. Landfall Navigating  4. Live Reckoning  5. Point of No Return  6. Simplexity Aloft  7. Gathering Range  8. Shoot the Moon  9. Wages of Flight 10. Which way, Amelia? Air-Race  What is the best cruise altitude for winning in the skies?   Canard Advantage  Why put the horizontal stabilizer in the nose? Cleared to Land   One too many rules. Flyer Fatality  Wright Flyer tragedy: first in history but not the last. Flying Off the Grid  Electrical propulsion without stationary source. Gathering Range  What works has limits, what does not work does not. Green Flight   When conservation trumps speed. Here Comes the Sun   Racing against the sun. Landfall Navigating   Overcoming one type of navigation error. Live Reckoning   Steering by stars and by radio. Pilot's Nightmare   No time for calculation or controversy. Point of No Return   Decision delayed is decision denied. Position and Hold    Controversial maneuver -- before takeoff. Shoot the Moon  In the daytime, celestial navigators have two celestial bodies, not one. Simplexity Aloft   Analysis of multiple, independent failures. Sloping in the Dark   Counter-intuitive, 'black hole' approach.  The Clock Won't Wait   As time goes by, so too does your position. V-Tail  Seeking information that is "not for public disclosure." Wages of Flight   Need to fly meets the need for speed. Which way, Amelia?   The greatest mystery in aviation history. Wind Circle    On the average, wind is not friendly to flight. Wingsuit Aerodynamics  How to maximize gliding distance. World's Fastest Airliner   Super-sonic flight can spook cows and rattle school windows. Zero Mystery  In WWII, the Corsair was able to turn right faster than the Zero. Space Stuff   Égaré (French for 'stray') Collection 0. Astrogating Asteroids 1. Rock from the Sky 2. Orbital Deflection 3. Prepositions in Space 4. What Goes Around 5. Plural Gravities 6. Extinction Avoidance Astrogating Asteroids Discovery for avoiding a collision course with Planet Earth. Aurora Borealis  An amazing photograph no matter how you look at it. Barycenterfold  Object lesson provides perspective on solar system dimensions. Corner-Cube   Good enough may sometimes be better than perfect. Ellipse Illusion  Ellipse in a cylinder is intuitive, but in a cone, not so much. Extinction Avoidance  Preventing what will eventually happen. How Many Planets? Historically named versus unknown or unnamed. Martian Microbe  Exciting discrepancy in genetic codes.  Measuring the Moon  A penny for your perspective. Mystery Orbit  Space invention in search of a necessity. Orbital Deflection  Invention for the deflection of a threatening asteroid. Plural Gravities  Reality for asteroids goes beyond Keplerian Laws Pocket Rocket Analysis of an elegant concept for achieving Inertial Propulsion. Prepositions in Space Which way is 'up' and how long until 'next'? Rock from the Sky  Strategem for avoiding collision with a Near Earth Object (NEO) To Billow or Not to Billow  Cloudy evidence for "dark matter" in space. Trampoline Deorbiting System  Satellite with sacrificial derelict capturing mechanism. Trappist Orbits  Seven exoplanets in harmonious stability. What Goes Around  Figuring out arrival times at an orbital intersection. Words and Meanings Collective Nouns  Matching the names for groups of things with the things.  Figures of Speech   Names for expressions matched with what the expressions express. Groaner of the Third Kind   Classification of jokes, some funny but not all.  Largest Prime Number   Like everything else, numbers need names. Omancy Schmancy   Twenty methods for figuring out the future. Palindromes for All Times   Historical and humorous reversibilities. Paradigm Shift  Wresting one's presumptions from one's grasp. Put-Down Noun   Proper terminology for expressing scorn, polite or otherwise.  Riddle from Hell   Finding the impact of nothing on everything. Riddle?...or Hoax!  On crooked postulations by juveniles and jokesters. Surgical Precision   Ungiven toast on a napkin. Syllables of Recorded Time   Conservation by acronym and abbrev., supposedly. Techword Puzzle   First of its kind, probably for a good reason. Wholly Toledo   Challenging creative children on long car-trips. DISCLAIMER: All images found on this site are believed to be in the public domain. If any image herein is published on your website and you do not want it to be displayed here, or if you want Puzzles with a Purpose to feature a link to your website, then please contact paul@niquette.com to request the appropriate action.