Monthly Archives: September 2017

Puzzle #197: 10 Friends

Posted on September 24, 2017 by Alok Goyal

This is a very common puzzle, many variants of which one would have. I still like it as the answer is very elegant, and teaches children a methodology. This one is from Mathematical Circles (Russian Experience) by Dmitri Fomin, Sergey … Continue reading →

Posted in Puzzles | Tagged , | 3 Comments

Solution to Puzzle #195: 1989!

Posted on September 24, 2017 by Alok Goyal

I received many correct answers. These included  Suman Saraf, Vishal Poddar and Anand Sanghi. Thank you and well done! This puzzle can be solved using the concept of “invariants” and parity. Note that for any numbers a and b (a … Continue reading →

Posted in Solution | Tagged , , | Leave a comment

Puzzle #196: Bugs on a Board

Posted on September 17, 2017 by Alok Goyal

Yet another very fine puzzle from A Moscow Math Circle: Week by Week Problems by Sergey Dorichenko. Each square of a 9 x 9 board has a bug sitting on it. On a signal, each bug crawls onto one of … Continue reading →

Posted in Puzzles | Tagged , , | 1 Comment

Solution to Puzzle #194: Adjacent Cells on a Chessboard

Posted on September 17, 2017 by Alok Goyal

I got only two correct answers for this puzzle – from Suman Saraf and Pratik Poddar – thank you both and well done! I am taking the liberty of copying the answer from Pratik – I find it to be … Continue reading →

Posted in Solution | Tagged , | Leave a comment

Puzzle #195: 1989!

Posted on September 10, 2017 by Alok Goyal

This is a beautiful puzzle from Mathematical Circles (Russian Experience) by Dmitri Fomin, Sergey Genkin and Ilia Itenberg. There numbers 1, 2, 3, ….. , 1989 are written on a blackboard. It is permitted to erase any two of them … Continue reading →

Posted in Puzzles | Tagged , , , | 4 Comments

Solution to Puzzle #193: Smallville Telephones

Posted on September 10, 2017 by Alok Goyal

This was a simple puzzle, and I got correct answers from many. These include Vishal Poddar, Pratik Poddar, Suman Saraf, Mahi Saraf and Anand Singhi. Well done all. The answer is “Not Possible”. This is a simple application of graph … Continue reading →

Posted in Solution | Tagged , | Leave a comment

Puzzle #194: Adjacent Cells On a Chessboard

Posted on September 2, 2017 by Alok Goyal

This is another beauty of a puzzle from A Moscow Math Circle: Week by Week Problems by Sergey Dorichenko. The numbers from 1 to 64 have been placed in each square on a chessboard such that each number appears exactly … Continue reading →

Posted in Puzzles | Tagged , , | 1 Comment

Solution to Puzzle #192: Too Many 6’s

Posted on September 2, 2017 by Alok Goyal

This was a difficult manipulation of numbers, and I received 4 answers from Mahi Saraf, Anand Singhi, Pratik Poddar and Prakhar Prakash. Only two of these I found to be completely correct – from Mahi Saraf and Anad Singhi. That … Continue reading →

Posted in Solution | Tagged , | 1 Comment