Been awhile since I've been in school, so forgotten a lot, and I came across a problem that I having trouble figuring out.
Looking for the formulas so I can understand it.
Given 100 people randomly choosing a number from 1 - 100, what is the probability that exactly 3 people will have picked the same number.
Same as above but instead what is the probability that at least 3 people will have picked the same number.
I can do it with small numbers doing probability trees but obviously with 100 numbers and 100 people the number of combinations would be large. Would prefer a formula that would be able to calculate the answer(s).