Re: Tricky maths problem

From: Bob Silverman (anonymous_at_mathforum.org)
Date: 08/20/04 

Date: Fri, 20 Aug 2004 19:07:29 +0000 (UTC)

On 20 Aug 2004, Stephen J. Herschkorn wrote:
>Tristan wrote:
>
>>Johnny has a coin, he tells Billy that he will give him £10 every time he spins heads, but take £5 off him every time he spins tails. What are the chances that Billy will have a positive amount after 5 spins? And after 10 spins? After X spins?
>>
>Let N be the number of heads out of x spins. (Do Brits really spin
>coins? Americans toss them). How large ust N be for Billy to have a
>positve amount? What is the distribution of N?

A minor nitpick:

The question, AS ASKED, can not be answered.

Why?

Because it did not state that "Johnny has a FAIR coin".

The question can not be answered without knowing the bias, if any.

Relevant Pages

  • Re: Tricky maths problem
    ... Let N be the number of heads out of x spins. ... Americans toss them). ... How large ust N be for Billy to have a ...
    (sci.math)
  • Re: Slot Question
    ... each spin is an independent event. ... Not under this three coins only scenario. ... an marginal added payout possibility from the extra two coins to ... You triple your chance of hitting something with three spins instead of one. ...
    (alt.vacation.las-vegas)
  • Re: Bayesian estimation of Expectation in Bernoulli problem
    ... Choose one of the coins at random and imagine spinning it repeatedly. ... Given that the first two spins from the chosen coin are tails, ... Let N be the number of additional spins until a head shows up ...
    (sci.stat.math)
  • Bayesian estimation of Expectation in Bernoulli problem
    ... I would be interested in a hint, a pointer or some help with the ... Choose one of the coins at random and imagine spinning it repeatedly. ... Given that the first two spins from the chosen coin are tails, ... Let N be the number of additional spins until a head shows up ...
    (sci.stat.edu)
  • Bayesian estimation of Expectation in Bernoulli problem
    ... Choose one of the coins at random and imagine spinning it repeatedly. ... Given that the first two spins from the chosen coin are tails, ... Let N be the number of additional spins until a head shows up ...
    (sci.stat.math)