Binomial Formula is just this:
(a + b)^n = (nC0)a^n + (nC1)a^(n-1)*b + (nC2)a^(n-2)*b^2 + ... + (nCn)b^n
where a, b can be anything.
Binomial probability refer to cases where there are several incidents (flips of a coin, # marbles out of a bucket, etc) to be considered, each independant of previous ones (e.g. even if you happen to get 100 heads in a row, the 101th flip will still be 1/2 probability heads, and 1/2 tails). Most important is that there are only two choices (e.g. heads or tails, black or white, left or right, etc)
Example: there are 10 black counters, each labelled "2", and 5 white counters, each labelled "3", in a container.
Bob draws 4 counters (and remembers what they were), each time replacing before the next draw.
Find the probability that:
a) The sum of the numbers is 9
b) The sum of the numbers is at least 10
c) The sum of the numbers is odd.
{Hint: the total probability is 1, so you might like to express 1 = (10/15 + 5/15)^4 }
