Question

In how many ways can we choose a 12 member jury from 30 possible people?

Answer 1

This is a problem dealing with permutations and combinations.
Order does not matter in this problem.
Since order doesn't matter, it is a combination.
Repetition matters, since you can't have the same person count as two people.

There are twelve slots.

_ _ _ _ _ _ _ _ _ _ _ _ 

Each slot needs to be multiplied by the next.

_*_*_*_*_*_*_*_*_*_*_*_

Now we have to fill in the slots.
Each slot will be filled with a number one less than the one before it. It has to be one less, since repetition matters.
The numbers will be decreasing from 30, since there are 30 possible people.

30 * 29 * 28 * 27 * 26 * 25 * 24 * 23 * 22 * 21 * 20 * 19

Multiply these numbers together and you get your answer.

41,430,393,164,160,000 ways