Logical ReasoningDifficulty: Easy

PT16 S2 Q6 Explanation

The introduction of symbols for numbers

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

TopicsNecessary Assumption

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Stimulus

The introduction of symbols for numbers is an event lost in prehistory, but the earliest known number symbols, in the form of simple grooves and scratches on bones and stones, date back 20,000 years or more. Nevertheless, since it was not until 5,500 years ago that systematic only then that any sort of computation became possible.

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
6.

Which one of the following is an assumption on which the

Answer choices

  1. Trap3% picked this

    Grooves and scratches found on bones and stones were all made by people, and none

  2. Trap7% picked this

    Some kinds of surfaces upon which numeric symbols could have been made in the period before 5,500 years ago were

  3. Trap1% picked this

    Grooves and scratches inscribed on bones and stones do not date back to the time

  4. Correct85% picked this

    Computation of any sort required a systematic method for

    Why this is right

    Answer D is correct.

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

  5. Trap5% picked this

    Systematic methods for writing numerals were invented only because the need

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