Unplugged Practice Test: Logical Reasoning Set 3, Question 13 (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
Consultant: Barring ultra-fast charging from delivery fleets will not end its use. The uptime gain it delivers is enormous, and the leading fleets will do whatever secures a gain that large. Ultra-fast charging should therefore be permitted, but only where a licensed inspector caps each pack's charge rate so that rates stay inside the range certified as safe. Run that way, the risk that a pack will catch fire goes away.
13. Which one of the following is an assumption required by the consultant's argument?
- (A)Customers would not think less of fleets known to be running ultra-fast charging.
- (B)Fleets now running ultra-fast charging are unable to find inspectors willing to cap their packs.
- (C)Charge rates above the certified range yield no large uptime gain over rates within it.
- (D)Ultra-fast charging would not raise some fleets' uptime more than it raises other fleets' uptime.
- (E)Fleets do not run ultra-fast charging in situations where it fails to raise uptime.
CWhy (C) is correct
The consultant's plan only removes the fire risk if capping the rate at the certified safe level doesn't cost fleets any of the uptime gain they're chasing. If charging above that range delivered a bigger gain, the same fleets who do whatever secures a large gain would keep pushing past the cap, and the risk wouldn't disappear. (C) rules that out: rates above the certified range yield no larger gain than rates inside it, exactly what the capped plan needs.
Why the other answers are wrong
AWhy (A) is wrong
(A) worries about customer opinion, a concern the argument never raises.
BWhy (B) is wrong
(B) asks whether current fleets can already find willing inspectors, not whether the capped plan removes the incentive to exceed it.
DWhy (D) is wrong
(D) compares fleets to each other, but the plan doesn't depend on every fleet gaining the same amount.
EWhy (E) is wrong
(E) claims fleets never charge fast when it wouldn't help, which says nothing about whether a cap removes the reason to push past it.
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.
