Logical Reasoning · Necessary Assumption

PrepTest 103 · Section 2 · Question 7

Phase 1 (your first ~400 questions): read the guidance, then answer. No clock.

Step 1 · Pre-Question Guidance · read this first

Question type

Necessary Assumption

The one idea it tests

The argument says a plan is impossible because one way of doing it fails, so it must assume the other ways do not count.

The basic logic

Ask what the plan actually requires, and what the argument shows is impossible. If the argument rules out only one shape of solution, it needs a hidden plank saying other shapes would not satisfy the plan.

Tiny words that decide it

“cannot”
“hence”
“single”

Playground logic

Ms. Rivera says the art club kids should get their own table group. Marcus says it is impossible because the art kids sit in far-apart corners and no single connected block of desks would have mostly art kids. Secret sauce: a 'table group' made of scattered desks would not count; pull that plank and the argument falls.

Step 2 · The kid story

The Art Club Table

Ms. Rivera announced, 'The art club kids should have their own table group, where art club members are the majority.' Marcus shook his head. 'Impossible! Art club kids sit in three corners of the room. If you push together one connected block of desks that includes them all, you also get tons of non-art kids. So it cannot happen.' Priya raised her juice box. 'Marcus, what if the art group is three little desk clusters, one in each corner, and we just call them one group?' Marcus blinked. 'That doesn't count. A group has to be all in one piece.' Lulu wrote: 'Marcus assumes a split-up group would not count.' 'Yes,' said Marcus. 'Obviously.' 'It is not obvious,' said Lulu. 'It is your secret sauce.'

Step 3 · Try the model question

Ms. Rivera suggests giving art club members their own table group in which they are the majority. But art club members sit in scattered corners, and no single connected block of desks can include them while keeping them the majority. So Marcus concludes the suggestion cannot be met.

Marcus's reasoning needs which one of these to be true?

Step 4 · The courtroom tale

The Bird Sanctuary Map

A wildlife board ordered that the red-wing marsh birds receive their own protected zone where they outnumber other birds. A developer's lawyer argued, 'Your Honor, these birds nest in four marshes miles apart. Any single unbroken zone big enough to cover them all would be full of other birds. The order cannot be obeyed.' Mr. Whitfield, for the board, tugged his suspenders. 'Counsel assumes the zone must be one unbroken piece. Our order never said so. Four separate protected patches would satisfy it.' The judge nodded. 'Then counsel's whole argument rests on that unstated point. If patches count, the order can be met.'

Step 5 · Work the real question

Open PrepTest 103, Section 2, Question 7 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the conclusion (the plan cannot be satisfied) and the evidence (one particular way of carrying it out fails). Ask what gap sits between 'this way fails' and 'every way fails.' Use the Pull the Plank test on each choice: negate it and see whether the conclusion collapses. The right choice, when negated, opens a door the argument ignored. Drop choices about history, feelings, or extra requirements stronger than the plan asks.