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Monthly Archives: September 2014
Puzzle #76: What’s The Final Digit?
A beautiful puzzle for ages 10100! Found this in Mathematical Circle Diaries, Year 1 (for grade 57), 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
Solution to Puzzle #75: Clock Reflection
Thanks for the response to this puzzle. I got correct answers from three people – Ashutosh Diwakar, Rajeev Deshpande and Pallav Pandey in that order. Well done! I am also taking the liberty of replicating Ashotosh’s solution which I thought was … Continue reading
Puzzle #75: Clock Reflection
Here is a nice clock problem I found on a web site, originally created by Lewis Carroll. A clock has hour and minute hands of the same length and no numerals on its face. At what time between 6 and … Continue reading
Solution to Puzzle #74: Overlapping Clock Hands
Apologies for not posting the answer last weekend, I was traveling. This was perhaps too simple a puzzle, and that is why I did not get a response from anyone! The correct answer is 22. An easy way to think about … Continue reading
Puzzle #74: Overlapping Clock Hands
This is a relatively simple puzzle, more geared for children than for adults. My friend Alok Mittal recently asked this question in his Mathematical Circles class and also reminded me that he was asked this puzzle (probably 30 years back!) … Continue reading
Solution to Puzzle #73: Find the Two Numbers
This was a difficult puzzle. Many people sent me the answers, though none of them were completely correct. One grade 11 student sent me the correct answer but the reasoning was not completely correct. So unfortunately no names on the … Continue reading