BTGmoderatorDC wrote:At a certain school, is the number of biology students greater than the number of chemistry students?

(1) Of the biology students, 30 percent are also chemistry students.
(2) Of the chemistry students, 40 percent are also biology students.

OA C

Source: Princeton Review

Say there are B number of biology students and C number of chemistry students.

We have to determine whether B > C.

Let's take each statement one by one.

(1) Of the biology students, 30 percent are also chemistry students.

=> Number of ONLY biology students = 70% of B = 0.7B and number of biology & chemistry students = 30% of B = 0.3B. Since we do not have any information about the number of chemistry students, we cannot compare B and C. Insufficient.

(2) Of the chemistry students, 40 percent are also biology students.

=> Number of ONLY chemistry students = 60% of C = 0.6C and number of biology & chemistry students = 40% of C = 0.4C. Since we do not have any information about the number of biology students, we cannot compare B and C. Insufficient.

(1) and (2) together

From both, 0.3B = 0.4C => B = 4/3 C => B > C. Sufficient.

The correct answer: C

Hope this helps!

-Jay
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