Select the correct answer.

Jim's sock drawer has two pairs of black socks, three pairs of white socks, one pair of green socks, and two pairs of gray socks. One evening, he randomly picks three socks and turns up with 1 black sock, 1 white sock, and 1 gray sock. Without putting back the socks he picked, he picks another sock randomly. What is the probability that he will have a complete pair?

A. [tex]$\frac{2}{13}$[/tex]
B. [tex]$\frac{11}{13}$[/tex]
C. [tex]$\frac{4}{13}$[/tex]
D. [tex]$\frac{1}{16}$[/tex]



Answer :

To solve the problem, let's break it down step by step:

1. Initial Socks Count:
Jim's sock drawer contains the following pairs:
- 2 pairs of black socks: [tex]\(2 \times 2 = 4\)[/tex] black socks.
- 3 pairs of white socks: [tex]\(3 \times 2 = 6\)[/tex] white socks.
- 1 pair of green socks: [tex]\(1 \times 2 = 2\)[/tex] green socks.
- 2 pairs of gray socks: [tex]\(2 \times 2 = 4\)[/tex] gray socks.

Therefore, the initial total number of socks is:
[tex]\[ 4 \text{(black)} + 6 \text{(white)} + 2 \text{(green)} + 4 \text{(gray)} = 16 \text{ socks} \][/tex]

2. Socks Picked by Jim:
Jim picks 1 black, 1 white, and 1 gray sock. After picking these socks, the remaining socks are:
- Black socks: [tex]\(4 - 1 = 3\)[/tex]
- White socks: [tex]\(6 - 1 = 5\)[/tex]
- Green socks: [tex]\(2\)[/tex] (unchanged)
- Gray socks: [tex]\(4 - 1 = 3\)[/tex]

So the total number of socks left after Jim picks three socks is:
[tex]\[ 3 \text{(black)} + 5 \text{(white)} + 2 \text{(green)} + 3 \text{(gray)} = 13 \text{ socks} \][/tex]

3. Favorable Outcomes:
To complete a pair, Jim needs to pick either another black, white, or gray sock. The count of these socks is:
- Black socks: [tex]\(3\)[/tex]
- White socks: [tex]\(5\)[/tex]
- Gray socks: [tex]\(3\)[/tex]

Thus, the number of favorable outcomes is:
[tex]\[ 3 \text{(black)} + 5 \text{(white)} + 3 \text{(gray)} = 11 \text{ favorable socks} \][/tex]

4. Probability Calculation:
The probability that Jim will pick a sock that completes a pair is the number of favorable outcomes divided by the total number of remaining socks:
[tex]\[ \text{Probability} = \frac{\text{Number of favorable outcomes}}{\text{Total number of remaining socks}} = \frac{11}{13} \][/tex]

Therefore, the correct answer is:
[tex]\[ \boxed{\frac{11}{13}} \][/tex]