Puzzle #140: How far will Mr Bodger walk to dodge dirt?

#140 Drum roll

Aiming to mix the contents of a rusty drum without getting dirty, Mr Bodger has an idea. The drum is lying on its side, so he wants to place one end of an old plank, which is 5 metres long, on the side of the drum, then walk towards the drum while holding onto the plank. In this way, he will use the plank to roll the drum (without any slipping with respect to both the ground and the plank) to mix its contents. He will stop walking when he reaches the drum.

In fact, Mr Bodger…