Unplugged Practice Test: Logical Reasoning Set 1, Question 3 (Necessary Assumption)
Taking the test? Finish it first. This page shows the answer.
- Necessary Assumption questions ask for the unstated premise the argument depends on.
- Try the negation test. If negating a choice wrecks the argument, that choice is the necessary assumption.
- 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
The Verlin data center operated in the Corrand district for 6 years, during a period when the surrounding region suffered chronic electricity shortages. People lived and worked in Corrand throughout those years, but no other power-intensive business ever operated in the district. Any unallocated grid capacity in Corrand would have drawn such businesses to the district. So the company that owned the Verlin center must have generated the center's electricity itself, and that company was therefore not solely a provider of data services.
3. Which one of the following is an assumption on which the argument depends?
- (A)Unless its owner generates its electricity, a data center is unlikely to operate in a district that has no unallocated grid capacity.
- (B)With access to on-site generation, other power-intensive businesses could have operated in the Corrand district.
- (C)A data center whose owner generates its electricity consumes less power than a comparably sized data center drawing from a grid.
- (D)Building on-site generation is one of the first steps a company must take when it expands from data services into the sale of electricity.
- (E)No company that generates its own electricity also draws electricity from a public grid.
AWhy (A) is correct
The argument leans on one gap: no other power-intensive business ever ran in Corrand, and any spare grid capacity would have pulled one in. That only proves Verlin generated its own power if a data center couldn't have run there on grid power alone once the grid had nothing spare left. (A) supplies exactly that: unless its owner generates its own electricity, a data center is unlikely to operate where there's no unallocated capacity. Since Corrand plainly had none to spare, Verlin's 6 years of operation only make sense if its owner built its own generation.
Why the other answers are wrong
BWhy (B) is wrong
(B) talks about what other businesses could have done with access to on-site generation, not about how Verlin itself kept running, so it's beside the point.
CWhy (C) is wrong
(C) compares power consumption between self-generating and grid-drawing centers, which the argument never needs to settle.
DWhy (D) is wrong
(D) describes a step a company takes when it moves into selling electricity, a different question from why Verlin generated power for its own use.
EWhy (E) is wrong
(E) claims no company both generates and draws from a public grid, far stronger than the argument requires.
Common questions
What type of question is this?
Necessary Assumption. Necessary Assumption questions ask for the unstated premise the argument depends on.
How do I get better at Necessary Assumption questions?
Try the negation test. If negating a choice wrecks the argument, that choice is the necessary assumption. The free LSAT cheat sheet lists the wrong-answer patterns to watch for on every type.
