1967 AMC 12 Problem 28

Attempt Problem 28 of the 1967 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 1967 AMC 12 solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

28.

Given the two hypotheses: I Some Mems are not Ens and II No Ens are Vees. If “some” means “at least one,” we can conclude that:
Some Mems are not Vees
Some Vees are not Mems
No Mem is a Vee
Some Mems are Vees
Neither (A)(A) nor (B)(B) nor (C)(C) nor (D)(D) is deducible from the given statements
Answer: E
Concepts:logical deductionVenn Diagramcounterexample
Small hint:
Translate the three kinds of objects into sets M,N,VM,N,V
Big hint:
Test both M=VM=V and M∩V=∅M\cap V=\varnothing while keeping the two hypotheses true
Solution:
The hypotheses say only that some element of MM lies outside N,N, and that N∩V=∅.N\cap V=\varnothing. A model with M=VM=V makes (A), (B), and (C) false while satisfying the hypotheses. A model with M∩V=∅M\cap V=\varnothing makes (D) false. Hence none of choices (A) through (D) is forced.
Therefore, the correct answer is E.
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