For this one i have no idea what formula or even how to set it up...
Tow 6-sided dice are rolled. What is the porbability that the sum of the two numbers on the dice will be greater than 9?
Notation: n1 is the number that die 1 shows, n2 is the number that die 2 shows.
Then we want to know in how many ways you can have:
n1 + n2 > 9
1 <= n1 <= 6
1 <= n2 <= 6
We know that without restrictions there are 36 possibilities (both n1 and n2 can then take 6 values), so we have to divide the number of possibilities by 36.
In this case the number of possibilities is not that large and you can just count all possibilities:
n1 = 4, n2 = 6
n1 = 5, n2 = 5
n1 = 5, n2 = 6
n1 = 6, n2 = 4
n1 = 6, n2 = 5
n1 = 6, n2 = 6.
by anychance do you know of a good website where it shows a similar example of how to use this type of formula....
I think the best thing you could do is study discrete mathematics from a good textbook.
I just found this PDF file: