The Student Room Group

Simple Moddy Probability Question

Afternoon all - I was hoping someone here could settle an argument among some of the mods. :tongue:

There are 60 volunteers on the mod team, and about 10 of those are Section Leaders.

Suppose I select two mods at random (without replacement). What's the probability that both are SLs?

Based on my understanding of the old "balls in a bag" example, I'd have thought it'd be 10/60 x 9/59 = 9/354. However, one member of the team (who shall remain nameless!) is saying something about the groups being "linked", so it's a case of conditional probability.

It's been about 6 years since I've studied any maths, so please could someone shed some light on the right answer?

Thanks a lot!
(edited 9 years ago)
Are s leaders also mods?
Original post by keromedic
Are s leaders also mods?


Yes.
Someone more experienced will comment but I think the events are independent.

P (S|M)=P (S) so I'd agree with your answer Blackacre
I got following your multiplication rule thing: (10/60) x (9/59) = 90/3540 which simplifies to 3/118?

But I now see and agree with your methods :p:
(edited 9 years ago)
Your method is right, Mr Blackacre :kiss: :awesome:

I wonder who the rogue mod was :innocent:
(edited 9 years ago)

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