Ant Walk
Inspired by a question at http://math.stackexchange.com/questions/133851/ant-in-a-circle
An ant is sitting in the middle of a circle of radius 3 meters. Every minute, the ant picks a random direction and moves straight 1 meter.
On average, how long does it take the ant to leave the circle?
More GeoGebra at mathhombre.blogspot.com.