The study of probability may be thought of as a study of random outcomes or risk. Probability is useful in analyzing games of chance, business risk, market analysis, life insurance, finance, government policy planning, and scientific studies, to name a few. While it is a relatively young field in mathematics, its applications are far reaching into nearly every aspect of human life. Probability, like statistics, has its own particular language of terms and symbols that you’ll need to spend time with in this module. Much of the mathematics of probability involves fractions, which you have studied in previous sections. Nevertheless, it will be good to spend some time preparing for this module with a review of ratios and arithmetic on fractions, particularly with regard to adding and subtracting fractions. Since it is often desirable to view probabilities in fraction form rather than converting to decimals to compute them, you’ll also see a technique for finding the least common multiple involving prime factorizations that may prove useful. We’ll end the review module with a preview of finding the probability of an event to help you practice fractions in context.