I’ve been posting fortnightly puzzles in the Guardian for almost a year now, and one of the trickiest things to judge is level of difficulty.
I try only to set puzzles that are understandable to everyone, and that at least a significant minority will be able to solve.
But judging by the comments I think today I may have set the bar too high.
The challenge with Bongard problems is to find the rule that applies to the six left-hand images, and the rule that applies to the six right hand ones, which is often the negation of the left hand rule.
All the rules are easy to explain - but even so it is extraordinarily difficult to find them. As you have been discovering....
If you got all five correct consider yourself a genius.
LEFT: Three points in a line. RIGHT: No three points in a line
LEFT: Black region widens towards the centre. RIGHT: Black region narrows towards the centre.
LEFT: Midpoints of lines collinear. RIGHT: Midpoints of lines not collinear.
LEFT: One circle passes through the centre of the other circle. RIGHT: Neither circle passes through the centre of the other circle.
LEFT: End points of line and dot make an isoceles triangle (i.e where two sides are of equal length). RIGHT: End points of line and dot make a scalene triangle (i.e where all side lengths different).
Thanks to Harry Foundalis.
I post a puzzle here on a Monday every two weeks.
My most recent book is the mathematical colouring book Snowflake Seashell Star. (In the US its title is Patterns of the Universe.)
You can check me out on Twitter, Facebook, Google+ and my personal website.
And if know of any great puzzles that you would like me to set here, get in touch.
