There is a puzzle which I remember from many years ago which can be summarised as

> It is easy to arrange 20 items in five rows of four items, but how could you arrange just 10 items in five rows of four items?

The answer is this (spoiler-protected for those of you who want to try to solve it first):

>! ![enter image description here][1]

which is all very clever, but what is the more general case of this lateral thinking puzzle?


  [1]: https://i.sstatic.net/Pujkw.jpg