Blog Post #59: Family Fun!

Dear Readers,

I would like to share with you some good fun that I recently sent to my whole family, for we have no less than five birthdays coming soon!

My two sisters, one niece, my son, and my nephew will be turning 54, 49, 17, 21 and 21 respectively.

I told them that I have thought of three different whole numbers. The PRODUCT of my three numbers equals the total of 54+17+21. However, the SUM of my three mystery numbers equals 49.

Your fun challenge is to figure out exactly what my three mystery numbers are.

I also have a wee dose of chess for you…

Black (to move) has an invisible knight somewhere on the d- or e-file.

Your chess challenge is to determine the optimal square for the invisible knight so that Black can then force checkmate as quickly as possible.

Solutions will be published on the day of my next blog post, and in the meantime I wish you a wonderful weekend now.

With all best wishes,

Paul Motwani.

Puzzle Solutions (being posted on 4.10.2019)

Maths: The three mystery numbers are 1, 2 & 46.

Chess: With an invisible knight on d2, Black forces checkmate in four moves with 1…Nb3+ 2 Kb1 Qf5+ 3 Rc2 Qf1+ 4 Rc1 Qxc1#.


Author: Paul A. Motwani

My name is Paul Motwani, but my colleagues, my students and their parents mostly call me "Mr. Mo"! My middle initial, A, stands for Anthony, because I was born on the official feast day of St. Anthony of Padua, the patron saint of miracles and of lost souls. I love teaching Mathematics and Chess, and giving fun-packed talks and shows in schools and clubs. The popular ingredients of Math, Chess, Mystery and Magic are my "Fantastic Four", and I give prizes too! I am an International Chess Grandmaster, and (loooooong ago!) I was the World Under-17 Champion. I am the author of five published chess books and hundreds of newspaper articles. I live with my wonderful wife and son in Belgium. I also love music, movies and puzzles. I blog at My e-mail address is You can find me on Facebook, too.

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