L2
Ants on a Rod
Senior Quant · Brainteasers & Logic
100 ants, 1 cm/s, random directions. Ants reverse on collision. Expected time for all to fall off?
Question
100 ants are placed randomly on a 1-metre rod, each walking at 1 cm/s in a random direction. Ants reverse direction on collision (equivalent to passing through each other). What is the expected time for all ants to fall off? What is the maximum possible time?