Baron Mount Chance
Author: Scott Farrar

Drag the red point to see dynamic data.

Extending this to an equation, running an x number of times
results in a f(x) = 1 - .99^x chance.
f(x) is in black, 100% chance is plotted in green.
Notice no matter how many times you kill Baron, you will never reach 100%.

WoWhead reports a 1% drop chance.
If you run one time, you have a 1/100 chance.
If you run two times,
you have not a 2/100 chance, but rather
1 - (1 - 1/100) * (1 - 1/100) = 1 - .99 * .99

The expected probability of having Baron Rivendare's Mount drop:

f(x) = 1 - 0.99^(x)
a = 1
g(x) = 1
DragMe = Point(f)
b = OrthogonalLine(DragMe, xAxis)
c = OrthogonalLine(DragMe, yAxis)
Chance = Intersect(c, yAxis)
Run = Intersect(xAxis, b)
d = Segment(Chance, DragMe)
e = Segment(Run, DragMe)
h: x(Run)
i: y(Chance)
j: round(h)
text4: "After run # " + j
text5: "You will have a " + (i 100) + "% chance of seeing the mount drop."