Nob’s number puzzle


Virtual Assistant, Web Design and bookkeeping services

Child psychologists have long since recognised that children learn through games and play. Being in control in play helps them to learn to manage their feelings and when children make or build things in their play, the are building skills and confidence in themselves and in the relationship with others.

Similarly, for adults, challenging yourself to solve problems creatively is a great way to exercise your brain. And mathematics can be, if you make it to be, fun. Dean Burnett (2013) wrote in his article for the Guardian, “Mathematics is seen by many as hard, boring or both. But evidence suggests that a love of maths is no barrier to fun and humour, although a poor understanding of maths can have unpleasant consequences.”

This next puzzle shows how basic maths can be brilliant in its simplicity and is a tribute to the late Japanese puzzle guru Noboyuki Yashigahara or Nob as everybody used to call him in Japan. Nob graduated from the Tokyo Institute of Technology in applied chemistry and after turning down his career in high-polymer engineering, he became an educator of chemistry and mathematics. He thrived as a puzzle columnist and wrote over 80 books on puzzles.

He considered this puzzle as his masterpiece and I agree, it is brilliant. Give it a go, but please don’t cheat by finding the answer on the internet. You will be genuinely surprised and intrigued by its geniosity.

The numbers in the number tree are filled in according to a certain rule Try to find the missing number. It doesn’t require advance maths and no, there is no typo mistake. Have fun! The answer will be published in a few days time.


Bellos A. (2016) Can you solve my problem?, London, Guardian Books and Faber and Faber Ltd, available at

Burnett, D. (2013) ‘Maths is fun (sometimes)’, Guardian, 16 October [Online]. Available at

You May Also Like…

The barber paradox – Solution

The barber paradox – Solution

Suppose someone, let's call them John, has been found who wants to take on the role of national barber of Giwi....

Play Thinks

Play Thinks

Ivan Moscovich was a designer and commercial developer of games, toys and puzzles. Having survived two concentration...


Submit a Comment

Your email address will not be published. Required fields are marked *