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Author Archives: Alok Goyal
Solution to Puzzle #80: The Bored Guards
While the puzzle did not require any special mathematical knowledge, it was a relatively difficult puzzle and I did not get as many correct answers. The only correct asnwer was from Girish Tutakne. Here is a simple explanation – Number the … Continue reading
Puzzle #80: The Bored Guards
This is a beautiful puzzle from the book “Mathematical Circle Diaries, Year 1” by Anna Burago (Chapter 9, last puzzle). For parents of middle school children, this is a highly recommended book. At midnight, six guards assume their positions at … Continue reading
Solution to Puzzle #79: Diwali Special
This was a very nice puzzle and I got many responses, though only one of which was completely correct – from Girish Tutakne. What was commendable was that he sent his answer literally within a few minutes of my posting … Continue reading
Puzzle #79: Diwali Special
Since playing cards is very popular during the Diwali festival, here is a special probability puzzle with cards, contributed by Alok Mittal from his Mathematical Circles class. I heard this one last night and could not resist. I am breaking … Continue reading
Solution to Puzzle #78: Probability of #6
This was a tricky question…somewhat similar to the Monty Hall Problem (please see https://alokgoyal1971.com/2013/06/09/puzzle-20-the-monty-hall-problem-very-interesting-must-try/). I got a number of answers and a few of them correct in my opinion. The ones that sent the correct answers include Vishv Vivek Sharma (my … Continue reading
Puzzle #78: Probability of #6
This is a wonderful probability puzzle given to me by my nephew, Karan Sharma, who lives in Jaipur and is in Class XII – thanks Karan! A man is known to speak the truth 3 out of 4 times. He … Continue reading
Solution to Puzzle #77: Make the Stacks Equal
Apologies for not posting the solution last weekend, I was traveling outside the country. I received an overwhelming number of correct solutions for this puzzle. First one to come back was Alok Kucklous. Others were Aman Singla, Girish Tutakne, Ashutosh … Continue reading
Puzzle #77: Make the Stacks Equal
Another beautiful puzzle from the same book as last time…”Mathematical Circle Diaries, Year 1″, by Anna Burago. This one is the last puzzle from Session 10. Six stacks of coins are places on the table. The first has 1 coin, … Continue reading
Solution to Puzzle #76: What’s the Final Digit?
I received an overwhelming number of correct responses to this puzzle…though very few from the younger ones. Ones who gave the correct answers included Pooja Goyal, Naresh Kumra, Smiti Mittal, Prakhar Prakash, Girish Tutakne, Ashutosh Diwakar, Aishvarya Gupta, Ashish Gupta, … Continue reading
Puzzle #76: What’s The Final Digit?
A beautiful puzzle for ages 10-100! Found this in Mathematical Circle Diaries, Year 1 (for grade 5-7), Session 25, problem #8. Robby the Robot multiplied the numbers from 1 to 100 (100 factorial) and calculated the sum of the digits … Continue reading
Alok Goyal's Puzzles Page 