Unplugged Practice Test: Logical Reasoning Set 2, Question 10 (Must Be True)
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- These questions ask what must be true given the statements.
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The question
Ventilation report: A newly designed attic duct is built from short modules fitted end to end, each module carrying its own inline fan. Ducts of this kind sit no deeper than a standard joist bay allows. In a single-piece duct shallow enough for such a bay, the longer the duct runs, the weaker the airflow at its far end. Each module of a modular duct, though, is short enough that airflow through it stays strong. Moreover, any number of modules can be fitted together without weakening the airflow or deepening the duct.
10. The report's statements, if accurate, allow which one of the following to be properly inferred?
- (A)The modular design is unsuitable for an attic that needs only a short run of duct.
- (B)Modular ducts carry no drawbacks of any kind relative to single-piece ducts.
- (C)Ducts shallow enough for a standard joist bay can now be built to run very long and still move air strongly.
- (D)In an attic fitted with a single-piece duct, the deeper the duct sits, the stronger the airflow at its far end.
- (E)Homeowners want attic ducts that both run very long and move air strongly.
CWhy (C) is correct
The report says a single-piece duct shallow enough for a joist bay gets weaker airflow the longer it runs, but each module of a modular duct is short enough to keep its own airflow strong, and any number of modules can be joined without weakening airflow or deepening the duct. Put those together and (C) follows: a duct that still fits a standard joist bay can now run very long while still moving air strongly.
Why the other answers are wrong
AWhy (A) is wrong
(A) isn't supported; being able to join unlimited modules for a long run says nothing about whether the design suits a short one.
BWhy (B) is wrong
(B) overreaches, since the report only compares airflow and depth, not every possible drawback.
DWhy (D) is wrong
(D) goes beyond the report, which never ties a single-piece duct's depth to its airflow, only its length.
EWhy (E) is wrong
(E) isn't in the report at all; nothing there speaks to what homeowners want.
Common questions
What type of question is this?
Must Be True. These questions ask what must be true given the statements.
How do I get better at Must Be True questions?
Predict the answer before reading the choices. The free LSAT cheat sheet lists the wrong-answer patterns to watch for on every type.
