A student is randomly selected from this table. What is the probability that they are a freshman, given that they are a girl?

\begin{tabular}{|c|c|c|c|c|}
\hline \multicolumn{5}{|c|}{ Students on a Team } \\
\hline & Freshman & Sophomore & Junior & Senior \\
\hline Boy & 7 & 9 & 7 & 5 \\
\hline Girl & 5 & 5 & 4 & 2 \\
\hline
\end{tabular}

[tex]\[ P(\text{Freshman} \mid \text{Girl}) = \frac{\square}{\square} \][/tex]

[tex]\[ P(B \mid A) = \frac{P(A \text{ and } B)}{P(A)} \][/tex]

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Answer :

To find the probability that a randomly selected student is a freshman given that they are a girl, we need to follow these steps:

1. Determine the Total Number of Girls:
First, we sum the number of girls in each class (Freshman, Sophomore, Junior, Senior).
[tex]\[ \text{Total number of girls} = 5 + 5 + 4 + 2 = 16 \][/tex]

2. Identify the Number of Freshman Girls:
From the table, we see that the number of freshman girls is 5.

3. Calculate the Conditional Probability:
To find the probability that a student is a freshman given that they are a girl, we use the formula:
[tex]\[ P(\text{Freshman} \mid \text{Girl}) = \frac{P(\text{Freshman and Girl})}{P(\text{Girl})} \][/tex]
Here, [tex]\( P(\text{Freshman and Girl}) \)[/tex] corresponds to the number of freshman girls, and [tex]\( P(\text{Girl}) \)[/tex] corresponds to the total number of girls.

4. Substitute the Values:
[tex]\[ P(\text{Freshman} \mid \text{Girl}) = \frac{\text{Number of Freshman Girls}}{\text{Total Number of Girls}} = \frac{5}{16} \][/tex]

5. Simplify the Fraction:
After division, we get:
[tex]\[ P(\text{Freshman} \mid \text{Girl}) = 0.3125 \][/tex]

Therefore, the probability that a randomly selected student is a freshman given that they are a girl is [tex]\( 0.3125 \)[/tex].