Classics of Recreational Math

The classical recreational math authors are Lewis Carroll,  Henry DudleyMartin GardnerSam Loyd, and Yakov Perelman.

This an example of classical math puzzles: :

(102 + 112 + 122) – (132 + 142) = ?

The picture “Mental Count” of Russian painter Nikolay Bogdanov-Belsky contains the simple calculation. Image source : Wikipedia



Logical Reasoning in Pattern Recognition

Bongard problem is a kind of puzzle invented by the Soviet computer scientist Michael Bongard (1924–1971) in the mid-1960s. He died in 1971 during a hiking expedition in the Pamir Mountains. The tests played an important role in the disciplines of cognitive psychology and cognitive science. Human logical reasoning has a great advantage over computer intelligence.

Be smart.   Train your brain!

Here several problems similar to the original Bongard problems go:

What is the main difference between the pictures on the left page and on the right page?

A. z5461

B. z5462

C. z5468

Try to solve the problem yourself before looking for the answers  in the A+Click Brainteaser Problems.



Harry Foundalis collected hundreds of Bongard problems.


The logic puzzle almost everyone gets wrong

This is a very famous logic problem:

“Jack is looking at Anne, but Anne is looking at George. Jack is married, but George is not. Is a married person looking at an unmarried person?

  • A: Yes
  • B: No
  • C: Cannot be determined”


According to the Keith E. Stanovich in Scientific American more than 80 percent of people choose C, which is not the correct answer. The correct answer is A. Why?

This is another example of a similar problem:

There are only two handshakes in a meeting: John shakes hands with a person, this person shakes hands with Anna. Does a man shake hands with a woman in the meeting?


Dream Math

Everybody dreams.

rsauter-boyThe boy dreams of being an astronaut.

How long does he need to study and work until his dream can become reality?



Which job does not require math?


The photograph courtesy of Roland Sauter


Extraordinary Math Teaching by Dan Finkel

Dan Finkel suggested principles of extraordinary math teaching:

Math can the best of time or the worst of time.



1) Start with a question.

2) Thinking happens only when you have time to struggle.

3) (Teacher), you are not the answer key.

4) Say yes to your students’ ideas.

5) Play!

A marvelous quotation is attributed to the most brilliant scientist of the modern age, Albert Einstein: “Play is the highest form of research.”




Project Starters

Challenging puzzlers to create a positive attitude to real projects.

Estimate or Calculate?

” in the real world, we constantly settle for estimates, whereas mathematics — see the SAT — demands that you get the answer precisely right.” – Andrew Hacker in The New York Times article “The Wrong Way We Teach Math


boy sitting on money, money concept

Estimate or Calculate?

My answer is one of them and do it fast.