This booklet is designed to give a thorough grounding in Probability Theory. A good understanding in this topic is essential for all those people who wish to go on and study Mathematics and other science subjects like, Physics, Chemistry and Engineering. Often the fundamental concepts like these are frequently not completely understood leading to confusion and often dissatisfaction and can result in people giving up on the subject altogether. This is a shame because such confusion can often be attributed to poor teaching or unexplained misconceptions. This series of booklets sets out to explain fully and clearly every step throughout with everything presented in an easy to understand format through a wide variety of fully worked solutions covering most exam type questions. This booklet is the Probability Theory module and contains the following Factorials Unions Intersections Mutually exclusive probabilities Independent probabilities Additive probabilities Multiplicative probabilities 23 fully worked solutions No of 28 Other booklets in this series will be published shortly so keep a lookout for these as they become available.