Probability of a reoccurring roll
So if I were to role a 20 sided die my chance of rolling a 20 or any number in that matter would be 5%. Now if you roll a 20 you can re-roll. What are the chances of me being able to roll the die 10 times? Would the probability stay 5%, or would it decrease with each roll?
In other words, what is the chance of me rolling a 20, ten times in a row.
Basically the probability of rolling the die twice is $0.05$, the probability of rolling the die three times would be the probability of rolling a 20 in the first roll and rolling a 20 in the second roll, these two event are independent, so the probability of them would be $0.05 \cdot 0.05$
Analogously the probability of rolling the die 10 times would be the probability of rolling a 20 in throws 1, 2, ... , 9 ; so it would be $ 0.05 ^9 \approx 1.95 \cdot 10^{-12}$
So the probability of getting a 20 in a certain roll is $0.05$ but the probability of getting a 20 in every roll from 1 to 9 (i.e rolling 10 times) would decrease.