Monthly Archives: September 2013

Complete the alphabet (4)

1) Complete the alphabet*


In which row does the letter Z go?

If you solved it, we have the solution

This brainteaser was published in the British magazine “Games and Puzzles”.

Pattern codes – circles

1) Circles**
pattern code circle

Which code belongs at the question mark?
If you wish, you can peek at a hint

I have long suspected that there is a strong connection between mathematics and puzzles. Proving such a relation according to the scientific standards is of course another matter. It was nice to read that a study by the University of Chicago found that puzzle play helps boost Learning Math-Related skills in children between ages 2 and 4.

square sums

1) 3×3
Every row and column adds up to 50
Complete the square with the indicated numbers – those who have been given are already crossed out for you.

2) 4×4
Every row and column adds up to 50

3) 5×5
Every row and column adds up to 100.

This type of puzzle was published in Cijfervaria, a publication of Sanders Puzzelboeken. As I write this, they just published issue 5. Though I missed issue 4, I see they regularly publish Soduko variants, Binairo, Triairo, hitori, and battle ship.

You can check your solution here, here and

Did you know…
Learning new tasks saves brain cells – even if these tasks are more or less similar to already known tasks.

Four fours





Using exactly four fours, create the numbers 0-30. You may use the usual mathematical operands, but not squaring, as this requires a number 2. You may use brackets.
Example: (4+4)-(4+4)=0

As always, please don’t publish your solutions. Solutions can be found after 1-2 weeks on the solution page for those who want to check their solutions, or for those who are really stuck.
But scrolling is much easier, and really spoils the fun for others.

I am very much interested in your solution times, and I welcome your remarks and criticisms. Pointing out alternative solutions is also welcome, as they point out possible problems in the brain teasers.

If you are puzzled, we have a solution for you.

This puzzle has a long history. When I still was a teenager, my father challenged me to make all numbers 0-20 using the digit 4 exactly 4 times. Recently I shared this puzzle with some fellow consultants. Kees Krol arrived at the office one morning and announced he had extended the range all the way to 30. 🙂