What is the range of probabilities?
The probability of an event that is impossible is 0 and the probability of an event that is certain is 1. The probability of any event occurring falls within these two numbers as a decimal, if it is not impossible or certain. These videos will help you understand the range of probabilities in Prelim Standard Math.
The video below explains this in more detail.
How to calculate probabilities
The following video explains how to calculate probabilities when given certain information by a question.