Three men go into a shop to buy a TV.

They each have £10 on them and find a TV for £26.

They each give the shop attendant their £10.

The shop attenddant gives them back £1 each and to avoid the problems of splitting £1 three ways, he keeps the last pound to himself.

Now each of the three men have spent £9 and the shop keeper has kept £1 so that's 9+9+9+1 = 28.

The question is, where has the other £2 gone?