You take ONE roll of a 20-sided number cube to determine your fate. If you roll a number greater than or equal to 8 , you are able to defeat the troll. But if you roll a prime number, the bridge will give out with you still on it. What are Orgoth's chances of safely reaching the other side of the canyon?
There are 20 possible outcomes when rolling a 20-sided number cube.
Of those 20 outcomes, there are 12 that are greater than or equal to 8.
There are 8 prime numbers on a 20-sided number cube: 2, 3, 5, 7, 11, 13, 17, and 19.
Therefore, there are 8 outcomes that would cause the bridge to give out.
To find Orgoth's chances of safely reaching the other side of the canyon, we need to find the probability of rolling a number greater than or equal to 8 and subtract the probability of rolling a prime number.
Probability of rolling a number greater than or equal to 8: 12/20 = 0.6
Probability of rolling a prime number: 8/20 = 0.4
Therefore, Orgoth's chances of safely reaching the other side of the canyon are:
0.6 - 0.4 = 0.2 or 20% chance of success.