Suppose someone comes onto the site and is bored. That person starts spreading the rumor that levik is a monkey at exactly noon (on day 1) by sending an e-mail to one random person.

Then, each person sends an e-mail about this rumor (at exactly noon, on day 2) to one person. They can send it to anyone on perplexus (but themselves), even if that person already knows the rumor, or even if it was the person who told them about it.

Each successive day at noon, everyone that knows about the rumor sends a message to one other random person.

On average, on what day will everyone know about the rumor if there are 40 people (including the one that spread the rumor initially) at perplexus while the rumor is still spreading?

What if there were x people at perplexus while the rumor is still spreading?

(In reply to question by Perk)

Yes, a small chance and there's a small chance that every phone call will be to someone who has not yet heard the rumor. These represent the two extremes. That's why the question asked "on average." It's just like when you flip a coin 100 times there is a small chance that you will get 100 heads, and a small chance that you will get 100 tails. But most often, you will get some of each. On average, you will get in the range of 75 heads, 25 tails to 25 heads, 75 tails, approaching 50 of each.

Posted by TomM on 2004-05-01 01:21:41