## Intermediate Algebra (6th Edition)

We found in problem 86 that the probability of an event happening that is sure to occur is 1. In other words, $P(x)=1$ tells us that there is a 100% chance that event x will happen, because the number of ways that x can occur is equal to the number of possible outcomes. Therefore, the numerator and the denominator of the probability formula will be equal to each other, which will reduce to 1.