What's the probability of selecting John and then James as disciples of Jesus?

[mathdad]

Jesus had 12 disciples. What's the probability of selecting John and then James?

What is the set up?

 

[HallsofIvy]

Basically, you keep asking same question over and over again! Are you actually learning anything?

If you have n objects, the probability of choosing anyone of them is 1/n. If you have n objects, once you have chosen one, without replacement, there are n- 1 objects left. The probability of choosing anyone of those n- 1 objects is 1/(n-1). When the probability of event A is p and the probability of event B is q, the probability of "event A and event B" is pq.

Here n= 12. The probability of choosing "John" first is 1/12. The probability of choosing "James" next is 1/11. The probability of choosing "John" and then "James" is 1/(11*12)= 1/132.

 

[mathdad]

Thank you very much.

 

[Jameson]

Hey RTCNC,

I do agree that this question is similar to the one you asked yesterday, so for me that only highlights the fact that you should work with us step-by-step to truly understand these problems. If someone just solves it for you, you won't be able to easily transfer that to other problems. Why don't you post what you've tried and your thoughts on it? Do you agree with what I'm saying conceptually?