This document defines probability and provides methods for calculating probabilities of simple events. It explains that probability is a measure of how likely an event is to occur, ranging from impossible (0%) to certain (100%). Examples of expressing probabilities as fractions, decimals, and percentages are given. The document also provides a formula for calculating probability as the number of possible outcomes of an event divided by the total number of possible outcomes. An example of flipping a coin and calculating the probability of getting heads is shown. Students are instructed to practice probability calculations in their textbook and notebooks.