All freshmen, sophomores, juniors, and seniors attended a high school assembly. The total student attendance is shown in the table below.

\begin{tabular}{|c|c|}
\hline
Class & Number of People \\
\hline
freshmen & 31 \\
\hline
sophomores & 10 \\
\hline
juniors & 17 \\
\hline
seniors & 22 \\
\hline
\end{tabular}

Twice during the assembly, a student is chosen at random to assist with the presentation. After the first student has finished assisting, the student returns to the group and can be chosen a second time.

What is the probability that the first student chosen is a senior and the second student chosen is a sophomore?

A. [tex]$\frac{11}{320}$[/tex]

B. [tex]$\frac{3}{80}$[/tex]

C. [tex]$\frac{11}{40}$[/tex]

D. [tex]$\frac{2}{5}$[/tex]



Answer :

Certainly! Let's work through the problem step by step.

First, we need to determine the total number of students who attended the assembly. We do this by summing the number of students from each class:
- Freshmen: 31
- Sophomores: 10
- Juniors: 17
- Seniors: 22

Adding these together:
[tex]\[ 31 + 10 + 17 + 22 = 80 \][/tex]

So, there are a total of 80 students.

Next, we calculate the probability that the first student chosen is a senior. There are 22 seniors out of the 80 students. Thus, the probability [tex]\( P(\text{senior}) \)[/tex] is:
[tex]\[ P(\text{senior}) = \frac{22}{80} = 0.275 \][/tex]

The first student then returns to the group, so the total number of students remains 80. Now, calculate the probability that the second student chosen is a sophomore. There are 10 sophomores out of the 80 students. Thus, the probability [tex]\( P(\text{sophomore}) \)[/tex] is:
[tex]\[ P(\text{sophomore}) = \frac{10}{80} = 0.125 \][/tex]

Finally, to find the combined probability that the first student chosen is a senior and the second student chosen is a sophomore, we multiply these two probabilities:
[tex]\[ P(\text{senior and sophomore}) = P(\text{senior}) \times P(\text{sophomore}) = 0.275 \times 0.125 = 0.034375 \][/tex]

To express this probability as a fraction, we see that:
[tex]\[ 0.034375 = \frac{11}{320} \][/tex]

Thus, the probability that the first student chosen is a senior and the second student chosen is a sophomore is:
[tex]\[ \frac{11}{320} \][/tex]

Therefore, the correct answer is:
[tex]\(\frac{11}{320}\)[/tex].