Blog Post #88: 39916800 Surprises for Herman & Others!

Dear Readers,

Based on the high number of jokes that I’ve cracked with my students, my colleagues and the school leaders at Musica Mundi School, some of them concluded (correctly) that my wife and my family must be “very courageous” to bear with such humour at home, too!

I was planning to say to Headmaster Herman that I’m only going to teach subtraction from now on because I just want to make a difference, but he’d have to deduct more points from my dossier…though I might be gifted a high-speed, one-way trip to the moon!

Lunar jokes rock, and these are inspired by the fact that (not counting where the little apostrophe ‘ thingy is), HERE’S MR LUNAR is one of 39916800 possible rearrangements of the letters in HERMAN’S RULER !

OK, it’s time to sharpen up our Maths skills, but we’ll still allow calculators!

  1. Start with 63, a number that Herman likes.
  2. Multiply it by 88, in honour of this Blog Post #88.
  3. Now multiply by 7200, in recognition of the number of seconds that Herman heroically bore with my jokes in one two-hour session!

The result is a reminder that there’ll be lots more laughs pouring down…

…and I hope I’m not alone in that!

To be serious for a moment–and MO meant it!–the number 88 is rather special. Its square has no isolated digits occurring alone: 88 squared = 88 x 88 = 7744. Eighty-eight is the smallest positive whole number with that property.

Now for something fresh ‘n sneaky…

Use the chart above (which highlights prime numbers smaller than 100) to find four consecutive prime numbers whose total sum (when you add them up together) is 88.

That challenge is preparing you for the next one…

Warm congratulations if you found 17, 19, 23 and 29.

17 + 19 + 23 + 29 = 88, and that’s the absolute largest-possible two-digit sum that we can get by adding four consecutive prime numbers.

We now come to a beautiful, fascinating, further challenge! I hope that all readers will enjoy it very much, and there’s a bonus prize possibility for anyone at Musica Mundi School, as well as for other students whom I work with personally, if they email a good-quality solution to me by 10:00am Central European Time (CET) tomorrow morning (Sunday 7 February)!

The solution will be posted (God-willing as always) tomorrow…


I’m thinking of a special secret positive whole number right now…Let’s call it X. If I add my secret number X to each of the prime numbers 17, 19, 23 and 29, I get four different consecutive prime numbers.

Your fun challenge is to discover the precise value of my secret number, X…

Wishing everyone lots of fun now, and a wonderful weekend too,

Paul Motwani xxx

P.S.=PUZZLE SOLUTION! (being posted now on Sunday 7 February 2021)

Warm congratulations again to Louise (a very clever student of mine) and to the multi-talented Depute Headmistress at Musica Mundi School for finding that X=24. (I can’t resist noting that X is the 24th letter of the English alphabet, and also 24=(my favourite number 3 x this blog post number 88)/my house number 11, but now I’ll give a real third reason…!)





A nice way of visually spotting the solution is to look again in the Prime Numbers chart given earlier…

Notice the 2-4-6 differences from 17 to 19 to 23 to 29.

Further down in the chart, where exactly can we again find the 2-4-6 differences…?

They occur with 41 to 43 to 47 to 53, and those prime numbers are 24 more than the primes that we started with.

Most sincerely, I wish you a joyful, peaceful 24 hours now this Sunday and every day xxx



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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