How to guess whether a certain region is inside a closed curve or outside
it when a part of the curve is not visible? Is there any clear and simple
method to do this?
This is a puzzling number tree in which when you already think the
solution is in your pocket you suddenly realize it slipped out because
of a "tiny digital typo". Don't believe? Just give it a try!
It can be a little Christmas puzzle gift to entertain you for a few
minutes at least - only three triangles hidden in a Christmas Tree and the
extra one that has to be found.
Remove some coins from a big coin triangle containing ten coins and a lot
of smaller equilateral triangles so that no equilateral coin triangles
remain.
Color the points of a "web"
into two colors - red and blue - in such a way that do not allow any
sequence of three points of the same color be found in a single line.
