A bag contains six identical black balls. A boy withdraws one ball from the bag without looking into it. What is the probability that he takes out:
a white ball?

Answer

To solve the problem, we need to determine the probability of the boy withdrawing a white ball from a bag that contains only black balls.

### Step-by-step Solution:

1. **Identify the Total Number of Balls:**
- The bag contains a total of 6 balls.
- All of these balls are black.

2. **Identify the Number of Favorable Outcomes:**
- We are interested in the event of drawing a white ball.
- Since there are no white balls in the bag, the number of favorable outcomes (drawing a white ball) is 0.

3. **Calculate the Probability:**
- Probability is calculated using the formula:
\[ \text{Probability} = \frac{\text{Number of Favorable Outcomes}}{\text{Total Number of Outcomes}} \]
- Here, the number of favorable outcomes is 0 (since there are no white balls) and the total number of outcomes is 6 (the total number of balls).
- Therefore, the probability of drawing a white ball is:
\[ \text{Probability} = \frac{0}{6} = 0 \]

4. **Conclusion:**
- The probability that the boy takes out a white ball is 0.