1959 AMC 12 Problem 47

Attempt Problem 47 of the 1959 AMC 12 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1959 AMC 12 solutions, or check the answer key.

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47.

Assume that the following three statements are true:

I. All freshmen are human.

II. All students are human.

III. Some students think.

Given the following four statements:

(1)(1) All freshmen are students.

(2)(2) Some humans think.

(3)(3) No freshmen think.

(4)(4) Some humans who think are not students.

Those which are logical consequences of I, II, and III are:

22

44

2,2, 33

2,2, 44

1,1, 22

Answer: A
Concepts:logical deductioncounterexample
Difficulty rating: 1320
Small Hint:

Use the person whose existence is asserted in statement III

Big Hint:

Combine “some students think” with “all students are human”

Solution:

Statement III supplies at least one student who thinks. By statement II, that student is human, so some human thinks and statement (2)(2) follows. Nothing relates freshmen to students, says whether freshmen think, or guarantees a thinking human outside the students. Thus none of (1),(1), (3),(3), or (4)(4) follows.

Therefore, the correct answer is A.

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Problem 47 in Other Years

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