All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars
 perplexus dot info

 Bird on a Wire (Posted on 2004-06-07)
A telephone wire stretched tight between two poles placed ten meters apart is a favorite resting spot for a flock of crows.

Suppose one morning two crows land on the wire, each at a random spot (the probability is uniformly distributed). With a bucket of paint and a brush you mark the stretch of wire between them. A certain length of wire will have been painted.

On average, what length of wire would you expect to have painted? Assume that each bird is a single point along the line, and so has no width.

Suppose instead that a dozen crows landed on the wire, each at an independent, random location, and you painted the stretch of wire between each bird and its nearest neighbor. On average, what total length of wire would you expect to have painted now?

And if a thousand crows landed?

A computer-generated solution could be found, but bonus points will be awarded for a formal proof!

 No Solution Yet Submitted by Sam Rating: 3.7000 (10 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
 re(3): Full solution | Comment 35 of 42 |
(In reply to re(2): Full solution by Bon)

No Bon,

Charlie is correct, there may be gaps.

Take the simpler case of four birds which land at points 1, 2, 8, and 9.

According to the rules of the problem, the region between 2 and 8 will not be painted.

 Posted by ThoughtProvoker on 2004-07-30 06:22:34

 Search: Search body:
Forums (0)