Question

In Robert's grade, 1/3 of the students have a sister. Of the students who have a sister, 1/2 also have a brother. What fraction of the students in Robert's grade have both a sister and a brother?

Answer 1

Answer:

1/6 of the students in Robert's grade have both a sister and a brother.

Explanation:

Let x be the number of total students in Robert's grade.

It is given that In Robert's grade, 1/3 of the students have a sister.

Number of students have a sister = $\frac{1}{3}\times x=\frac{x}{3}$

Of the students who have a sister, 1/2 also have a brother.

Number of students have both a sister and a brother = $\frac{1}{2}\times \frac{x}{3}=\frac{x}{6}$

We need to find the fraction of the students in Robert's grade have both a sister and a brother.

$\frac{\frac{x}{6}}{x}=\frac{1}{6}$

Therefore, 1/6 of the students in Robert's grade have both a sister and a brother.