Paddy goes to work painting white lines on the motorway with a tin of paint and a brush, after the first day he accomplishes 4 mile... later that day his boss congratulates him.
The next day Paddy paints 2 miles of white lines... so his boss said, "yeh that's acceptable."
On the third day he only does 1/4 of a mile... the boss says, "What's wrong you did 4 miles the first day?"
Paddy replies, "Yeh but the tin keeps getting further away"...