Raghu Pasupathy (from Shane Henderson)

100 ants (assume zero-length) walk at 1cm/second on a one-dimensional stick that is one metre (100 cm) long. When two ants collide, they both reverse direction. If an ant reaches the end of the stick, it falls off. What arrangement of ants maximizes the time before all ants have fallen off? How long can they last?

Solution to the Puzzle