Category Archives: Puzzles

Puzzle #109: Fox in a Hole

Posted on August 8, 2015 by Alok Goyal

A beautiful logic puzzle that I found on Gurmeet’s puzzle collection, which he has attributed originally to K Rustan M Leino at Microsoft Research. Consider five holes in a line. One of them is occupied by a fox. Each night, … Continue reading →

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Puzzle #108: The Double Square Number Problem

Posted on July 26, 2015 by Alok Goyal

While browsing through mind cipher.com, I came across this wonderful puzzle…a good puzzle for those who love to play with numbers. It’s said that a number N with 4 digits is a double-square number when it equals the sum of … Continue reading →

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Puzzle #107: The Longest Path

Posted on July 19, 2015 by Alok Goyal

I read this beautiful puzzle in the book “Invitation to a Mathematical Festival” by Ivan Yashchenko. Take a look at the figure below. A tourist wants to walk along the streets of Old Town from the train station (A) to … Continue reading →

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Puzzle #106: Cards and Two Magicians

Posted on July 11, 2015 by Alok Goyal

This is a very interesting puzzle contributed by Pallav Pandey – thanks Pallav! I have not solved it yet, and looking forward to working on it! Magician M1, calls an audience on stage who pulls random 5 cards from the … Continue reading →

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Puzzle #105: 150 Year Old Puzzle

Posted on July 4, 2015 by Alok Goyal

This is truly an old puzzle. I was sent this one by Salik Shah (thank you Salik). It appeared in the WIRED magazine. I am reproducing the puzzle verbatim as I saw it in WIRED: IN 1850, THE Reverend Thomas … Continue reading →

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Puzzle #104: Togglers Puzzle

Posted on June 7, 2015 by Alok Goyal

Another beautiful puzzle this time – one from my nephew Karan Sharma, originally seen from Khan Academy, though available at other places as well. This is a truth-liar problem. Here it goes: You are in a room with five people. … Continue reading →

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Puzzle #103: Proof Without Trigonometry

Posted on May 30, 2015 by Alok Goyal

This is a wonderful puzzle I found in the puzzle collection of The Guardian newspaper, the original source being Martin Gardner. The beauty of this puzzle is that one needs to use simple rules of geometry and we do not … Continue reading →

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Puzzle #102: The Persistence Puzzle

Posted on May 24, 2015 by Alok Goyal

This is yet another famous puzzle from the Martin Gardner collection. I was made aware of this one by my nephew, Karan Sharma – thank you! I have not looked up the answer to this one, so do not know … Continue reading →

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Puzzle #101: Shortest Path Touching the X-Axis…

Posted on May 17, 2015 by Alok Goyal

This is a beautiful puzzle initially sent to me a month back by Arunima, a friend from IIT Delhi now in Washington DC. The same puzzle was sent to me by another friend’s son, Amol Aggarwal, now doing his PhD … Continue reading →

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Puzzle #100: The 100 square rug puzzle (Prize Puzzle)!

Posted on April 26, 2015 by Alok Goyal

Never imagined when I started 2 years back that I will be posting 100 puzzles at some time…thanks to all readers for continuous engagement and encouragement! Here goes the 100th one…will reveal the original source when I post the answer. … Continue reading →

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