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 = [tex]\frac{1}{3}\times x=\frac{x}{3}[/tex]
Of the students who have a sister, 1/2 also have a brother.
Number of students have both a sister and a brother = [tex]\frac{1}{2}\times \frac{x}{3}=\frac{x}{6}[/tex]
We need to find the fraction of the students in Robert's grade have both a sister and a brother.
[tex]\frac{\frac{x}{6}}{x}=\frac{1}{6}[/tex]
Therefore, 1/6 of the students in Robert's grade have both a sister and a brother.
