Unplugged Practice Test: Logical Reasoning Set 2, Question 13 (Sufficient Assumption)
Taking the test? Finish it first. This page shows the answer.
- Sufficient Assumption questions ask for a premise that would guarantee the conclusion.
- Look for the choice that, once added, forces the conclusion. It often connects a term in the evidence to a term in the conclusion.
- Every question on this test is original, written to the same logical skeletons as real questions, and Steve checked every one himself before release.
The question
In lettering a storefront from a stock stencil, a sign painter widens each letterform to allow for the spread of paint across the surface being lettered. Also, unless the sign board is exactly the width for which the stencil was cut, the painter rescales the stencil so that the lettering fits that board exactly. So a licensed sign painter never merely traces a stencil, but always rescales it to fit the board exactly.
13. Which one of the following, if assumed, allows the conclusion above to be properly drawn?
- (A)Most stock stencils are cut without any allowance for the spread of paint across the surface being lettered.
- (B)Some of the painters who rescale stencils and widen letterforms are painters who hold a license.
- (C)Every board a licensed sign painter letters differs in width from the width for which the chosen stencil was cut.
- (D)The most skilled sign painters are the ones best able to rescale a stencil to the exact width of a board.
- (E)A licensed sign painter can always judge in advance, and to the fraction of an inch, how far paint will spread on a given surface.
CWhy (C) is correct
The conclusion says a licensed sign painter always rescales a stencil to fit the board exactly. But the stimulus only requires that rescaling unless the board happens to be exactly the width the stencil was cut for. That exception leaves a hole: if a licensed painter ever letters a board that matches the stencil's width precisely, no rescaling is called for, and always fails. (C) closes that hole by assuming every board a licensed painter letters differs from the stencil's cut width, so the exception never fires and rescaling always applies.
Why the other answers are wrong
AWhy (A) is wrong
(A) is about most stencils lacking any allowance for paint spread, which bears on the widening step, not on whether boards ever match a stencil's width.
BWhy (B) is wrong
(B) only says some painters who rescale and widen hold a license, which runs the wrong direction and can't force always for every licensed painter.
DWhy (D) is wrong
(D) ranks painters by skill at rescaling, a claim about who's best, not about whether the exact-match exception ever applies.
EWhy (E) is wrong
(E) concerns a painter's ability to judge paint spread in advance, which speaks to the widening step and leaves the exact-fit gap untouched.
Common questions
What type of question is this?
Sufficient Assumption. Sufficient Assumption questions ask for a premise that would guarantee the conclusion.
How do I get better at Sufficient Assumption questions?
Look for the choice that, once added, forces the conclusion. It often connects a term in the evidence to a term in the conclusion. The free LSAT cheat sheet lists the wrong-answer patterns to watch for on every type.
