Ten people are sitting around a round table. Three of them are chosen at random to give a presentation. What is the probability that the three chosen people were sitting in consecutive seats?
We have C (10,3) = 120 possible total selections of any three people
And there 10 possibilities of selecting 3 people who sit together
( The first group occupies seats 1, 2 and 3 and the last group occupies seats 10, 1 and 2)
So
1 2 3
2 3 4
3 4 5
.
.
.
10 1 2
So....the probability is just 10 / 120 = 1 /12