A bear goes for a walk. He walks 3 miles south, then 3 miles east, and finally 3 miles north. At the end of this walk the bear has arrived back where he started. What color is the bear?

What will be an ideal response?

The only point on earth that a walk of three miles south, three miles east and three miles north will return to the starting point is at the North Pole. The only type of bear that will be found at the North Pole is a polar bear. Therefore, the bear must be white.

We will ignore the issue of whether polar bears come as far north as the pole or if they are more likely to be found farther south near the edge of the ice cap where access to food is easier. Just consider that this a stray bear and the problem works very nicely.