What are the odds of rolling five ones with a dice in six tries?
You can do it in 6 ways:
11111x
1111x1
111x1x
11x111
1x1111
x11111
Each has the same probability: (1/6)5 x (5/6) = 1/6 x 1/6 x 1/6
x 1/6 x 1/6 x 5/6 = 5/46656
So the probability is 5/46656 x 6 = 5/7776
You can use the binomial theorem so answer more complex
questions like these.