This 'cake division by lines' problem was used as an example in one of the lectures I attended at business school.
I've searched and it doesn't seem to be on the site yet, so here it is:
You have a cake and a knife.
You may cut the cake, with the knife, three times, in any direction.
You may not break the cake into pieces with your fingers (it's unhygienic) or in any other way apart from using the knife.
Each cut must be in a straight line.
What is the maximum number of pieces into which you can cut the cake?
The pieces don't all have to be the same size.