Blog Post #60: For Sarah

Dear Readers,

Today’s post is for a friend named Sarah, who turned 48 yesterday. Your first fun puzzle is to figure out what is special about the italicized part in the following:

Yes, Friday afternoon! Mary has Art. Yay! One of my friends, Sarah,

can enjoy this puzzle with you, as well as the Maths and Chess brainteasers given below. Answers will be published at the time of the next post.

In celebration of Sarah’s Happy Birthday, your Maths challenge is to find positive whole numbers H and B for which 1 + H + B + H x B = 48.

We’ll say that H is greater than B. Then there are exactly four different solutions for H & B. Have fun finding all of them!

That’s quite fitting, because 48 is the largest positive whole number which equals four times the sum of its own digits.

Now it’s time for a wee dose of chess…

Quick checkmate!

White (to move) has an invisible knight somewhere on the f-file.

Your chess challenge is to determine the optimal square for the invisible knight so that after you place it on the f-file, White can then force checkmate as quickly as possible.

Beautiful Gardens

Wishing you a wonderful weekend now,

Paul Motwani.

SOLUTIONS TO PUZZLES (being posted now on 9.11.2019)

In Sarah’s word brainteaser, the first 25 letters in

Yes, Friday afternoon! Mary has Art. Yay! One of my friends, Sarah

exactly match the 25 letters in the second half!! In other words, the first 25 letters and the second 25 letters are anagrams of each other.

In Sarah’s Happy Birthday puzzle, the possible H, B pairs are:-

23, 1

15, 2

11, 3

7, 5

In the chess challenge, if we place a white knight on the square f5, then White can force checkmate with 1 Qh5+! Ke6 2 Qg6+ Rf6 3 Qxf6# or 1…Kg8 2 Nh6+! Kh7 3 Nf7+ Kg8 4 Qg6#.


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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