Logical ReasoningDifficulty: Easy

PT131 S3 Q12 Explanation

To cut costs

A free, expert breakdown of this official LSAT Logical Reasoning question.

TopicsNecessary Assumption

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Full official LSAT questions are available through LawHub. This page provides LSAT Lab's explanation, strategy, and review tools without republishing the full official question.

Stimulus

To cut costs, a high school modified its air­ conditioning system to increase its efficiency. The modified system, however, caused the humidity in the school air to decrease by 18 percent. Twenty-four hours after the decrease in air humidity, a 25 percent increase in the number of shows that a decrease in humidity can make people ill.

What this question is testing

Necessary Assumption

Your task

Find the assumption the argument requires in order for its conclusion to hold.

Common trap

Answers that would help the argument but aren't strictly required (sufficient, not necessary).

Winning move

Negate each choice — the right one breaks the argument when negated.

Reading along? Open the full official question in LawHub — we show a fragment here and keep the reasoning in our own words.

The question
12.

The argument depends on assuming which one of

Answer choices

  1. Correct83% picked this

    At least some of the visits to the school nurse after the system was modified

    Why this is right

    This connects the trips to the nurse’s office with students who are ill.

    Skill tested: Necessary Assumption · how this choice captures the argument's function is the move to repeat next time.

  2. Too Strong5% picked this

    Most of the students at the high school suffered from the decrease

    The argument does not rely on something being true for most of the students at the high school.

  3. Too Specific5% picked this

    It takes 24 hours after a person is infected with a virus for that person

    The argument does not need to connect being ill with a virus. Other pathogens make people ill as well. Furthermore, the 24 hour time period might line up with the argument but if time frame were a bit shorter, the argument would not be undermined.

  4. Too Strong5% picked this

    A decrease of 18 percent in air humidity causes an increase of 25 percent in one's

    The conclusion is that a decrease in humidity can make people ill, but it does not go so far as asserting the precise increase in likelihood one faces of becoming ill.

  5. Out of Scope1% picked this

    Modifying the air-conditioning system proved to be an ineffective way to

    Costs are not relevant to the argument.

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