Critical reasoning: what must be true

VerbalCritical reasoningEasy

All engineers at Firm X work remotely. Some engineers at Firm X are project managers. If the statements above are true, which of the following must also be true?

AAll project managers at Firm X are engineers.
BSome project managers at Firm X work remotely.
CMost engineers at Firm X are project managers.
DAll remote workers at Firm X are engineers.
ESome engineers at Firm X do not work remotely.

Try it before you scroll. Two minutes on the clock, then commit to an answer.

Correct answer: B

Chain the two statements. Some engineers are project managers, and every engineer works remotely. So those project managers who are engineers inherit the remote property: some project managers work remotely. That is (B).

A quick set picture helps: Engineers is a circle entirely inside Remote workers. Project managers overlaps the Engineers circle (that is what “some engineers are project managers” says). Any overlap with Engineers is automatically inside Remote, so PM ∩ Remote is nonempty.

Why the rest fail:

(A) reverses the overlap. Some engineers being project managers does not mean all project managers are engineers; the firm may employ non-engineer project managers.
(C) upgrades “some” to “most,” which the premises never support.
(D) reverses the first statement. All engineers work remotely, but other roles (designers, accountants) might work remotely too.
(E) flatly contradicts the first statement, which says all engineers work remotely.

On must-be-true questions, the correct answer is usually weaker and smaller than the traps. “Some project managers work remotely” commits to very little, which is exactly why it is guaranteed.

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