An old farmer was walking beside a tractor, which was driven by another farmer. The farmer driving the tractor was dragging a pipe behind him. The old farmer wants to figure out how long the pipe is. He starts by starting at the very end of the pipe (farthest away from the tractor) and walks forward until he reaches the other end of the pipe. This take 140 steps. He then walks back to the other end, which takes only 20 steps, as this time he is walking in the opposite direction of the tractor.
The tractor is moving constantly at a uniform speed. The farmer is also moving at a uniform speed, and each of his steps is one meter long.
How long is the pipe?