Let four Lines in a Plane represent four roads in General Position, and let one traveler be walking along each road at a constant (but not necessarily equal to any other traveler's) speed. Say that two travelers and have ``met'' if they were simultaneously at the intersection of their two roads. Then if has met all other three travelers (, , and ) and , in addition to meeting , has met and , then and have also met!

**References**

Bogomolny, A. ``Four Travellers Problem.'' http://www.cut-the-knot.com/gproblems.html.

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1999-05-26