Maths for Mums & Dads

The H-Coins puzzle

A little known puzzle that deserves to become a classic.


You might have heard of the famous Edwardian "9-Dots" puzzle (if you haven't, Google it).  In that puzzle,  the aim is to link all the dots with just four straight lines, without lifting your pen off the paper.  The solution spawned the modern cliche "thinking outside the box".

A couple of years ago, I was introduced to a coin puzzle by David Bedford which is reminiscent of the 9-dots puzzle - but I think it's even better. Here it is (this version appeared in the New Scientist puzzle column last year): 

 

Even those of us who know the nine dots puzzle take a while to solve the coins puzzle.  Finding one of the solutions is satisfying.  Finding both is even better.  

Spoiler - The two solutions are below:

 

*                               *                            *                          *                          *                              *

 

 

A case of thinking outside AND inside the box...