1. Let's start by stating the problem: Probability measures how likely an event is to happen. 2. The formula for probability of an event $E$ is given by: $$P(E) = \frac{\text{Number of favorable outcomes}}{\text{Total number of possible outcomes}}$$ 3. Important rules: - Probability values range from 0 to 1. - If $P(E) = 0$, the event never happens. - If $P(E) = 1$, the event always happens. 4. Example: If you roll a fair six-sided die, the probability of getting a 4 is: $$P(4) = \frac{1}{6}$$ 5. Explanation: There is only one favorable outcome (rolling a 4) and six possible outcomes (1 through 6). 6. If you want to find the probability of multiple events, you can use addition or multiplication rules depending on whether events are mutually exclusive or independent. 7. For example, the probability of rolling a 4 or a 5 is: $$P(4 \text{ or } 5) = P(4) + P(5) = \frac{1}{6} + \frac{1}{6} = \frac{2}{6} = \frac{1}{3}$$ 8. This is because rolling a 4 and rolling a 5 are mutually exclusive events. 9. To summarize, probability is a fraction or decimal that tells you how likely something is to happen, calculated by dividing favorable outcomes by total outcomes.