IDNLearn.com is your go-to resource for finding answers to any question you have. Get prompt and accurate answers to your questions from our community of knowledgeable experts.

The method 100 students use to get to school and their grade level is shown below.

[tex]\[
\begin{tabular}{|c|c|c|c|c|}
\hline & Drive & Bus & Walk & Total \\
\hline Sophomore & 2 & 25 & 3 & 30 \\
\hline Junior & 13 & 20 & 2 & 35 \\
\hline Senior & 25 & 5 & 5 & 35 \\
\hline Total & 40 & 50 & 10 & 100 \\
\hline
\end{tabular}
\][/tex]

Find the probability a student drives, given that they are a senior.

[tex]\[
P(\text{drives} \mid \text{senior}) = \frac{P(\text{drives and senior})}{P(\text{senior})} = [?]
\][/tex]

Round to the nearest hundredth.


Sagot :

To solve this problem, we need to find the probability that a student drives given that they are a senior. This is often written as [tex]\( P(\text{drives} \mid \text{senior}) \)[/tex].

We are given a table that shows the distribution of how the 100 students get to school according to their grade levels. Here is the table again for convenience:

[tex]\[ \begin{array}{|c|c|c|c|c|} \hline & \text{Drive} & \text{Bus} & \text{Walk} & \text{Total} \\ \hline \text{Sophomore} & 2 & 25 & 3 & 30 \\ \hline \text{Junior} & 13 & 20 & 2 & 35 \\ \hline \text{Senior} & 25 & 5 & 5 & 35 \\ \hline \text{Total} & 40 & 50 & 10 & 100 \\ \hline \end{array} \][/tex]

### Step-by-Step Solution:

1. Determine [tex]\( P(\text{senior}) \)[/tex]:

We need the probability that a student is a senior. We have 35 seniors out of a total of 100 students.
[tex]\[ P(\text{senior}) = \frac{\text{Number of seniors}}{\text{Total number of students}} = \frac{35}{100} = 0.35 \][/tex]

2. Determine [tex]\( P(\text{drives and senior}) \)[/tex]:

Next, we need the probability that a student both drives and is a senior. There are 25 such students out of a total of 100.
[tex]\[ P(\text{drives and senior}) = \frac{\text{Number of seniors who drive}}{\text{Total number of students}} = \frac{25}{100} = 0.25 \][/tex]

3. Calculate [tex]\( P(\text{drives} \mid \text{senior}) \)[/tex]:

We use the conditional probability formula:
[tex]\[ P(\text{drives} \mid \text{senior}) = \frac{P(\text{drives and senior})}{P(\text{senior})} \][/tex]

Substituting in the values we have determined:
[tex]\[ P(\text{drives} \mid \text{senior}) = \frac{0.25}{0.35} \approx 0.7142857142857143 \][/tex]

4. Round to the nearest hundredth:

The last step is to round the result to the nearest hundredth:
[tex]\[ 0.7142857142857143 \approx 0.71 \][/tex]

So, the probability that a student drives given that they are a senior is [tex]\( \boxed{0.71} \)[/tex].