Logical ReasoningDifficulty: Easy

PT134 S3 Q19 Explanation

The conventional process for tanning

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

TopicsNecessary Assumption

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Stimulus

The conventional process for tanning leather uses large amounts of calcium oxide and sodium sulfide. Tanning leather using biological catalysts costs about the same as using these conventional chemicals if the cost of waste disposal is left out of the comparison. However, nearly 20 percent less waste is produced with biological catalysts, therefore less costly to tan leather if biological catalysts are used instead.

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
19.

Which one of the following is an assumption required by

Answer choices

  1. Out of Scope1% picked this

    Leather tanned using the conventional process is not lower in quality than is leather tanned

    The quality of leather that is made using both processes is not relevant to the argument.

  2. Out of Scope4% picked this

    The biological catalysts that can be used in the tanning process are less costly by weight than are

    The weight of both biological catalysts and conventional chemicals is not relevant to the argument.

  3. Out of Scope2% picked this

    New technological innovations have recently made the use of biological catalysts in the tanning process

    A recent change in the cost of biological catalysts is not relevant to the argument.

  4. Correct81% picked this

    Disposal of tanning waste produced with biological catalysts does not cost significantly more than disposal of the same amount of waste

    Why this is right

    This provides a required relationship for tanning leather using biological catalysts to be less costly than using conventional chemicals.

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

  5. Too Strong11% picked this

    The labor costs associated with tanning leather using biological catalysts are not any greater than the labor costs associated

    The cost of tanning leather other than waste disposal is the same for both processes. Whether the line items in each set are exactly the same is not important, since the sum of those line items in both processes is the same.

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