8. Chairs. (From 7th grade, 1 point) A furniture store received a batch of office chairs. The chairs were identical in every way except for their colors: 15 chairs were black and 18 were brown. The chairs were in demand and were sold in random order. At some point, a customer on the store's website noticed that only two chairs were left for sale. What is the probability that these two chairs are of the same color?
Solution. We can assume that two random seats remain. Let's construct the experiment tree (Fig. 6). Event $A$ "the remaining seats are of the same color" is shown by the shaded oval. Its probability is

$$
\mathrm{P}(A)=\frac{15}{33} \cdot \frac{14}{32}+\frac{18}{33} \cdot \frac{17}{32}=\frac{43}{88} \approx 0.489
$$

Answer: approximately $0.489$.

![](https://cdn.mathpix.com/cropped/2024_05_06_11f8b78b86004d31b3e4g-04.jpg?height=457&width=646&top_left_y=1733&top_left_x=1276)

Fig. 6. Experiment tree[^2]