Logical ReasoningDifficulty: Easy

PT104 S4 Q9 Explanation

The only physical factor

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

TopicsNecessary Assumption

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Stimulus

The only physical factor preventing a human journey to Mars has been weight. Carrying enough fuel to propel a conventional spacecraft to Mars and back would make even the lightest craft too heavy to be launched from Earth. A device has recently been invented, however, that allows an otherwise conventional spacecraft to to go to Mars in a spacecraft that carries this device and then return.

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
9.

Which one of the following is an assumption on which the

Answer choices

  1. Trap6% picked this

    The amount of fuel needed for a spacecraft to return from Mars is the same as the amount of fuel needed to

  2. Trap8% picked this

    The fuel manufactured from the Martian atmosphere would not differ in composition from the fuel used

  3. Trap2% picked this

    The device for manufacturing fuel from the Martian atmosphere would not take up any of the

  4. Trap1% picked this

    A conventional spacecraft equipped with the device would not be appreciably more expensive to construct than

  5. Correct83% picked this

    The device for manufacturing fuel for the return to Earth weighs less than the tanks of fuel that a conventional spacecraft would otherwise need

    Why this is right

    Answer E is correct.

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

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