Combinatorics: Spreading Rumors and Probability

Click For Summary

Homework Help Overview

The problem involves a scenario where a rumor is spread among a fixed group of 10 people, with the question focusing on the probability that the original person, A, receives the third call after starting the rumor.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are exploring the interpretation of the problem, particularly regarding the fixed nature of the group and the implications for how the rumor can be spread. There is confusion about whether A can call anyone outside the group or if the calls must remain within the original ten people.

Discussion Status

Participants are actively questioning the assumptions of the problem, particularly the definition of the group of people involved in spreading the rumor. Some guidance has been offered regarding the fixed group of ten, but there remains uncertainty about the mechanics of the rumor spreading process.

Contextual Notes

There is a noted confusion regarding the setup of the problem, specifically whether the set of people who can be called remains constant or changes with each call. This has led to a humorous acknowledgment of the limitations of the problem's assumptions.

Shoney45
Messages
65
Reaction score
0

Homework Statement


A rumor is spread randomly among a group of 10 people by successively having one person call someone, who calls someone and so on. A person can pass the rumor on to anyone except the individual who just called.

What is the probability that if A starts the rumor, A receives the third call?

Homework Equations


none



The Attempt at a Solution


I'm having difficulty getting started with this one. If person A starts the rumor, then the way the question is worded, it would appear that A could choose any ten people that happen to live on planet Earth who happens to own a telephone. So that's got me real confused and I don't know how to start.
 
Physics news on Phys.org
Hi Shoney45! :smile:
Shoney45 said:
A rumor is spread randomly among a group of 10 people by successively having one person call someone, who calls someone and so on.
…
If person A starts the rumor, then the way the question is worded, it would appear that A could choose any ten people that happen to live on planet Earth who happens to own a telephone. So that's got me real confused and I don't know how to start.

No, it means a fixed group of 10 people. :wink:
 
tiny-tim said:
Hi Shoney45! :smile:


No, it means a fixed group of 10 people. :wink:

Cheers Tiny Tim! And thanks for your smiles!

So are you understanding the problem to say that the set of people which can be called to spread the rumor to consists of only ten people? So in other words, if A starts the rumor, and then calls those ten people, are you understanding the question to mean that that set of people who can be called with the rumor is the same set of ten people who were just called and given the rumor, and so on for any successive calls?

It doesn't much sound like rumor spreading to me, but if that is the problem then I will go with it.
 
Hi Shoney45! :smile:
Shoney45 said:
It doesn't much sound like rumor spreading to me, but if that is the problem then I will go with it.

The people who set these questions only know approximately nine other people. :wink:
 
tiny-tim said:
Hi Shoney45! :smile:


The people who set these questions only know approximately nine other people. :wink:

Sweet! Well, I guess I'll wrestle with the problem under this set of shiny new asumptions.
 

Similar threads

Can Mathematical Models Predict the Winner in Ecolopolis' Mayoral Race?
  • · Replies 3 ·
Replies
3
Views
2K
MHB Rumor Propagation on a Small Island: Theoretical Analysis and Simulation Results
  • · Replies 1 ·
Replies
1
Views
3K
Probability and pedestrian wait time density function
  • · Replies 32 ·
2
Replies
32
Views
3K
Challenge Micromass' big probability challenge
  • · Replies 116 ·
4
Replies
116
Views
18K
Problem Involving Combinatorics and Probability
  • · Replies 5 ·
Replies
5
Views
13K
A conditional probability question on picking out chips from a bowl.
  • · Replies 3 ·
Replies
3
Views
10K
Rumour Spreading Probabilities
  • · Replies 12 ·
Replies
12
Views
2K
Solving Markov Chain Problem: Probability of Infection
  • · Replies 2 ·
Replies
2
Views
3K
Hypergeometric Distribution homework problem
  • · Replies 1 ·
Replies
1
Views
3K
Graduate Probability of finding a k-subset in a d-dimensional random
  • · Replies 2 ·
Replies
2
Views
2K