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18 Dec 2025, 09:00
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D
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Difficulty:
65%
(hard)
Question Stats:
55% (01:15) correct
45%
(01:29)
wrong
based on 231
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At a certain university, each of two advanced courses, Biology and Chemistry, has more than 25 students enrolled. Is there at least one student enrolled in both courses?
(1) Every student who is not enrolled in Biology is also not enrolled in Chemistry.
(2) Every student enrolled in Chemistry is also enrolled in Biology.
I31-08
(1) Every student who is not enrolled in Biology is also not enrolled in Chemistry.
(2) Every student enrolled in Chemistry is also enrolled in Biology.
I31-08
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18 Dec 2025, 10:00
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GMAT Club Official Explanation:
At a certain university, each of two advanced courses, Biology and Chemistry, has more than 25 students enrolled. Is there at least one student enrolled in both courses?
(1) Every student who is not enrolled in Biology is also not enrolled in Chemistry.
This means anyone in Chemistry must also be in Biology because if a student were in Chemistry but not in Biology, then that student would be a counterexample to the statement. Since such a student cannot exist, all students in Chemistry must also be in Biology. So every Chemistry student is also in Biology. Since Chemistry has more than 25 students, at least those 25+ students are definitely in both courses. Sufficient.
(2) Every student enrolled in Chemistry is also enrolled in Biology.
This says the same thing: anyone in Chemistry must also be in Biology because if someone belonged to Chemistry without belonging to Biology, the condition would be violated. Therefore every Chemistry student must already be a Biology student. So again, every Chemistry student is in both courses. Since Chemistry has more than 25 students, there are definitely students in both. Sufficient.
Answer: D.
General Discussion
18 Dec 2025, 09:21
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I. If a student is in Chemistry, then they must be in Biology. Since Chemistry has more than 25 students, all of them are also in Biology, so there is overlap.
Sufficient
II. Every Chemistry student is enrolled in Biology. Chemistry has more than 25 students, so those students are also in Biology. Overlap exists.
Sufficient
Answer: D
Sufficient
II. Every Chemistry student is enrolled in Biology. Chemistry has more than 25 students, so those students are also in Biology. Overlap exists.
Sufficient
Answer: D
