1. **State the problem:** We have an urn with 4 blue balls and 5 red balls. We want to find the probability of randomly selecting a blue ball. 2. **Formula for probability:** The probability of an event is given by $$\text{Probability} = \frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}}$$ 3. **Identify favorable and total outcomes:** - Number of favorable outcomes (blue balls) = 4 - Total number of balls = 4 (blue) + 5 (red) = 9 4. **Calculate the probability:** $$P(\text{blue ball}) = \frac{4}{9}$$ 5. **Interpretation:** This means if you randomly pick a ball from the urn, the chance it is blue is $\frac{4}{9}$, or about 44.44%.