A drawer contains 2 white socks, 5 blue socks and 3 brown socks. If the socks are not replaced when drawn, what is the probability of selecting a white pair followed by a blue pair? (No calculator permitted). A. 2/5 B. 1/3 C. 1/9 D. 1/10

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Answer:

To calculate the probability of drawing a white pair followed by a blue pair without replacement, you need to consider the probability of each step.

1. Probability of first drawing a white sock: 2 white socks out of a total of 10 socks (2 white + 5 blue + 3 brown).

\( P(\text{white}) = \frac{2}{10} \).

2. After drawing a white sock, the total number of socks is reduced to 9.

3. Probability of second drawing a white sock: Now there is 1 white sock left out of the remaining 9 socks.

\( P(\text{white again}) = \frac{1}{9} \).

4. Probability of third drawing a blue sock: There are 5 blue socks left out of the remaining 8 socks.

\( P(\text{blue}) = \frac{5}{8} \).

5. After drawing a blue sock, the total number of socks is reduced to 7.

6. Probability of fourth drawing a blue sock: Now there are 4 blue socks left out of the remaining 7 socks.

\( P(\text{blue again}) = \frac{4}{7} \).

To find the probability of the entire sequence (white pair followed by a blue pair), you multiply the individual probabilities:

\[ P(\text{white pair then blue pair}) = P(\text{white}) \times P(\text{white again}) \times P(\text{blue}) \times P(\text{blue again}) \]

\[ = \frac{2}{10} \times \frac{1}{9} \times \frac{5}{8} \times \frac{4}{7} \]

This simplifies to \( \frac{1}{84} \).

Therefore, none of the provided options (A. 2/5, B. 1/3, C. 1/9, D. 1/10) match the calculated probability. Please double-check the options or the problem statement.