jack and jason are in a community of 100 where 40 of them are going to have a trip, what's the probability that jack and jason to be selected?

Answer 1

To compute the odds of two events occurring you need to multiply the odds of the first event by the odds of the second. In this case, the first event is either Jack or Jason being selected for the trip. The first person has the odds of 40/100, or 2/5 once reduced, of being selected. However, either Jack or Jason have been selected, the odds change. Say Jack gets selected. Now there are only 99 people in the community to choose out of, and there are only 39 spots left, because Jack has already taken one. Therefore Jason's odds are 39/99 or 13/33 once reduced. Therefore the odds of both events occurring are (2/5) * (11/13)= 22/65