# Probability of two teams

1. Jan 30, 2009

### mamma_mia66

1. The problem statement, all variables and given/known data

suppose that 35 people are divided in a random manner into two teams in such a way that one team contains 10 people and the other team contains 25 people. What is the probability that two particular people A and B will be on the same team.

2. Relevant equations

3. The attempt at a solution

35 people team C contains 10 people, so the chance to be in this team is 2/7
team D contains 25 people, so the chance is 5/7
when person A is divided in team C , then there is a chance for person B, to be also in this team, namely 9/34(1 person is already divided)
when person B is divided in team D, then there is a chance for person B, to be also in this team, namely 24/34
so there are 2 cases
case 1 has a chance of 2/7*9/34=18/238
case 2 has a chance of 5/7*24/34=120/238
together this is 138/238=69/119 (=0.58) that they are in the same team (the chance is always bigger than 50%)

2. Jan 30, 2009

### kasse

Re: probability