1. **Stating the problem:**
A bag contains 8 identical red balls and an unknown number of white balls, say $w$. The probability of drawing a red ball initially is given as $\frac{10}{18}$. After adding 4 more white balls, we want to find the new probability of drawing a red ball.
2. **Initial probability formula:**
The probability of drawing a red ball initially is
$$P(\text{red}) = \frac{\text{number of red balls}}{\text{total number of balls}} = \frac{8}{8 + w} = \frac{10}{18}$$
3. **Solve for $w$:**
Cross-multiply:
$$8 \times 18 = 10 \times (8 + w)$$
$$144 = 80 + 10w$$
Subtract 80 from both sides:
$$144 - 80 = 10w$$
$$64 = 10w$$
Divide both sides by 10:
$$w = \frac{64}{10} = 6.4$$
4. **After adding 4 white balls:**
New number of white balls:
$$w_{new} = 6.4 + 4 = 10.4$$
Total balls now:
$$8 + 10.4 = 18.4$$
5. **New probability of drawing a red ball:**
$$P_{new}(\text{red}) = \frac{8}{18.4}$$
Simplify:
$$P_{new}(\text{red}) = \frac{8}{18.4} \approx 0.4348$$
**Final answer:**
The probability of drawing a red ball after adding 4 white balls is approximately $0.435$ or $\frac{8}{18.4}$.
Red Ball Probability 6399E5
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