Blog Post #73: Sneaky Surprises for Sacha!

Dear Readers,

Today we can enjoy sneaky puzzles in honour of Sacha, one of my son’s very best friends who had his birthday several days ago. I will say that his birthday was a particular whole number, n, days ago, and Sacha’s new age then was the square root of (500-n squared).

Your fun challenge is to figure out Sacha’s age on his birthday just past, and also his exact date of birth.

The birthday presents included a lovely chess set and books, and now we have a special bonus chess puzzle…

Imagine that Black has an invisible pawn somewhere on the e-file.

Your chess challenge is to determine exactly where on the e-file the black pawn should be so that, immediately after placing it there, it will be White to move and force checkmate in n moves. n is the same n that featured in Sacha’s birthday number puzzle above!

I wish you lots of fun now, and a wonderful weekend too!

Paul Motwani xxx

Scroll down for the

P.S.=Puzzle Solutions!




























Sacha turned 22 four days ago, and his exact date of birth is 31 August 1998.

With a black pawn on e4, White forces checkmate in at most four moves via 1 Qf8+ and then either 1…Ke5 2 Qf6# or 1…Kg5 2 Qf6+ Kh5 3 Qh6# or 1…Rf7 2 Qxf7+ Kg5 3 Qf6+ Kh5 4 Qh6# in the longest line.

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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