1. Problem: Calculate the theoretical probability of getting an odd number when rolling a fair dice. 2. Formula: The theoretical 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: - The total number of possible outcomes is the total number of equally likely outcomes. - Favorable outcomes are the outcomes that satisfy the event condition. 4. All possible outcomes when rolling a fair dice are: $\{1, 2, 3, 4, 5, 6\}$. 5. Favorable outcomes for getting an odd number are: $\{1, 3, 5\}$. 6. Number of favorable outcomes = 3. 7. Total number of possible outcomes = 6. 8. Calculate the probability: $$P(\text{odd number}) = \frac{3}{6} = \frac{1}{2}$$ 9. Final answer: The probability of getting an odd number when rolling a fair dice is $\frac{1}{2}$.