Answered

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Students in a class were surveyed about the number of children in their families. The results of the survey are shown in the table below:

\begin{tabular}{|c|c|}
\hline
Number of Children in Family & Number of Surveys \\
\hline
one & 9 \\
\hline
two & 18 \\
\hline
three & 22 \\
\hline
four & 8 \\
\hline
five or more & 3 \\
\hline
\end{tabular}

Two surveys are chosen at random from the group of surveys. After the first survey is chosen, it is returned to the stack and can be chosen a second time.

What is the probability that the first survey chosen indicates four children in the family and the second survey indicates one child in the family?

A. [tex]$\frac{1}{50}$[/tex]
B. [tex]$\frac{2}{15}$[/tex]
C. [tex]$\frac{3}{20}$[/tex]
D. [tex]$\frac{17}{60}$[/tex]


Sagot :

To determine the probability that the first survey selected indicates four children in the family and the second survey selected indicates one child in the family, we'll follow these steps:

1. Calculate the Total Number of Surveys:
To start, you need to find out the total number of surveys conducted. According to the table:

- One child: 9 surveys
- Two children: 18 surveys
- Three children: 22 surveys
- Four children: 8 surveys
- Five or more children: 3 surveys

Adding these together gives the total number of surveys:
[tex]\[ 9 + 18 + 22 + 8 + 3 = 60 \][/tex]

2. Calculate the Probability for Each Selection:
- Probability that the first survey indicates four children:
[tex]\[ \text{Probability (four children)} = \frac{8}{60} = 0.13333333333333333 \][/tex]
- Probability that the second survey indicates one child:
[tex]\[ \text{Probability (one child)} = \frac{9}{60} = 0.15 \][/tex]

3. Determine the Combined Probability:
The surveys are chosen with replacement, meaning the selections are independent events. Therefore, the combined probability is the product of the individual probabilities:
[tex]\[ \text{Combined Probability} = \left(\frac{8}{60}\right) \times \left(\frac{9}{60}\right) = 0.02 \][/tex]

4. Convert to a Fraction:
To convert the combined probability into a fraction:
[tex]\[ 0.02 = \frac{2}{100} = \frac{1}{50} \][/tex]

Thus, the probability that the first survey chosen indicates four children in the family and the second survey indicates one child in the family is:
[tex]\[ \boxed{\frac{1}{50}} \][/tex]