Coin Landing On Its Edge

I flip a fair Swiss franc* and it falls in mousse**. What is the probability that the coin stays on its edge after the mousse melts? 
*One Swiss franc is about 1 USD; diameter 23.20mm , thickness 1.55mm, weight 4.4g.  During a coin toss, the coin is thrown into the air such that it rotates edge-over-edge several times.
**A mousse (French ‘foam’) is a prepared food that incorporates air bubbles to give it a light and airy texture.


The probability  that the coin stays on its edge is about 4% for a Swiss franc and 5% for an American dime.

Such an outcome on a hard and flat surface is fairly unlikely, having been estimated at approximately 1 in 6000 tosses.



What is digital fluency?

Source: What is digital fluency?

The Importance of Recreational Math

“The body of recreational mathematics that Mr. Gardner tended to and augmented is a valuable resource for mankind.” –

Aplusclick project tries to destroy the border between the Common Core and the Recreational Math.

Liar’s Math

Aplusclick Pinocchio

Pinocchio lies

When Pinocchio lies, his nose gets twice as long. When he tells the truth, his nose gets 1 cm shorter.

Today, his nose was 1 cm long in the morning, and it is 100 cm long in the evening.

What is the least possible number of times he opened his mouth today?

True and Random

Two gods  are called True and Random. True always speaks truly and Random speaks randomly truly or falsely. You don’t know who is who.

Determine the identities of the gods by asking yes-no questions; each question must be put to exactly one god.aplusclickgods

Adapted from G. Boolos. ‘The hardest logic puzzle ever’, The Harvard Review of Philosophy (6), 1996.


You find the answers to the questions in Grade 12 questions at

Geek Puzzle Cards

Geek’s puzzle cards are made for geeks

Geek Puzzles Cards