In my kitchen I have this cylindrical recipient for salt. Have a guess: what is longer its circumference or its height?

At first sight you would say, it is the height. Let's compare! My hand stretches easily to the height of the recipient but is not big enough to wrap my fingers around it. Quite surprising: the circumference is longer than the height!

We all learned in school, how to compute the circumference of a circle: you multiply the diameter by that famous number \pi, which mathematicians invented just for that purpose and whose approximate value is 22/7. And since 22/7 is greater than 3, the circumference is bigger than three times the diameter. Keeping that in mind our result above is not so suprising any more. In fact, the height really looks like less than three times the width.

Of course, most people underestimate the length of the circumference. Next time in a pub, challenge your friends with that question. Bet a beer on it, then use a napkin, for example, to compare both lengths as I do in the pictures below... I am sure you will win your bet!

The height is smaller... ...than the circumference. Mathoman wins a beer!