11 Oct '06 12:13

Also an old one, but still good.

An indian is paddling his canoe upstream. (Make it a boy scout if you want to be PC).

At some point, his spare paddle falls into the water and drifts downstream without him noticing.

When he DOES notice tha he must have dropped it overboard, he turns his canoe around (instantaneously, of course, as in all puzzles) and now paddles downstream at the same relative speed to the stream as before.

After 20 minutes, he catches up with his paddle.

An observer on the bank noticed that during that time, the paddle had moved exactly one kilometer from the place where it was dropped.

What is the speed of the stream?

(See if you can figure out a simple, intuitive way without complicated Algebra)

An indian is paddling his canoe upstream. (Make it a boy scout if you want to be PC).

At some point, his spare paddle falls into the water and drifts downstream without him noticing.

When he DOES notice tha he must have dropped it overboard, he turns his canoe around (instantaneously, of course, as in all puzzles) and now paddles downstream at the same relative speed to the stream as before.

After 20 minutes, he catches up with his paddle.

An observer on the bank noticed that during that time, the paddle had moved exactly one kilometer from the place where it was dropped.

What is the speed of the stream?

(See if you can figure out a simple, intuitive way without complicated Algebra)