In a class of students, the following data table summarizes how many students have a brother or a sister. What is the probability that a student chosen randomly from the class has a sister?
Has a brother	Does not have a brother
Has a sister	8	4
Does not have a sister	2	6

To find the probability that a student chosen randomly from the class has a sister, we need to look at the total number of students who have a sister and divide that by the total number of students in the class.

### Step 1: Total number of students
To get the total number of students, we sum all the values in the table:

\[
8 \ (\text{has a brother and has a sister}) + 4 \ (\text{does not have a brother but has a sister}) + 2 \ (\text{has a brother but no sister}) + 6 \ (\text{neither has a brother nor a sister})
\]

\[
\text{Total number of students} = 8 + 4 + 2 + 6 = 20
\]

### Step 2: Number of students who have a sister
The students who have a sister are those in the first row of the table:

\[
8 \ (\text{has a brother and has a sister}) + 4 \ (\text{does not have a brother but has a sister}) = 12
\]

### Step 3: Probability calculation
The probability that a randomly chosen student has a sister is the ratio of students who have a sister to the total number of students:

\[
P(\text{Has a sister}) = \frac{12}{20} = \frac{3}{5}
\]

So, the probability that a student chosen randomly from the class has a sister is \( \frac{3}{5} \) or 0.6.

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Here are 5 related questions you can explore:
1. What is the probability that a randomly chosen student has both a brother and a sister?
2. What is the probability that a randomly chosen student has no siblings (neither a brother nor a sister)?
3. If a student has a brother, what is the probability they also have a sister?
4. What is the probability that a randomly chosen student does not have a brother?
5. If a student has no sister, what is the probability they have a brother?

**Tip:** When calculating probabilities, always make sure the total (denominator) accurately reflects the entire population or sample under consideration.

In a class of students, the following data table summarizes how many students have a brother or a sister. What is the probability that a student chosen randomly from the class has a sister?

Has a brother    Does not have a brother
Has a sister     8                      4
Does not have a sister    2              6

Explore how to calculate the probability that a randomly selected student from a classroom has a sister. The problem involves basic probability concepts, ratios, and real-world data interpretation. Suitable for students in Grades 6-8.

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