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

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

Step-by-step 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 =
`(1)/(3)* x=(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 =
`(1)/(2)* (x)/(3)=(x)/(6)`

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

`((x)/(6))/(x)=(1)/(6)`

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