Bunuel wrote:

Do at least 60 percent of the students in Pat’s class walk to school?

(1) At least 60 percent of the female students in Pat’s class walk to school.

(2) The number of students in Pat’s class who walk to school is twice the number of students who do not walk to school.

We need to determine whether at least 60 percent of the students in Pat’s class walk to school.

Statement One Alone:

At least 60 percent of the female students in Pat’s class walk to school.

We do not know how many male and female students are in Pat’s class, nor do we know the percentage of male students who walk to school. Thus, statement one is not sufficient to answer the question.

Statement Two Alone:

The number of students in Pat’s class who walk to school is twice the number of students who do not walk to school.

If we let n = the number of students who do not walk to school, then the number of students who do walk to school is 2n. Furthermore, the total number of students can be represented by n + 2n = 3n. Thus, the percentage of students who walk to school is:

(2n)/(3n) x 100% = 2/3 x 100% = 66.7%

Statement two is sufficient to answer the question.

Answer: B

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