Question

If 3 suspects who committed a burglary and 6 innocent persons are lined up, what is the probability that a witness who is not sure and has to pick three persons will pick the three suspects by chance? That the witness picks 3 innocent persons by chance?

Answer 1

The number of ways you can pick 3 people from 9 = 9*8*7 / 3*2*1 = 84

So chance of picking the 3 suspects = 1 / 84.

The number of ways to pick 3 from the 6 innocent people = 6*5*4 / 3*2*1 = 20

Chances of picking 3 innocent people = 20 / 84  or 5/21