Logical Reasoning · Necessary Assumption

PrepTest 136 · Section 2 · Question 2

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

When evidence matches a deliberate practice, the argument needs the evidence to have come from that practice and not from some later accident.

The basic logic

The patty is a physical clue that fits a known custom; the top bun says the object belongs to that custom. Ask: could something else have made the clue? The required assumption rules out that other cause. Use Pull the Plank: if the clue came from an accident, the conclusion falls.

Tiny words that decide it

“not”
“after”
“far from”

Playground logic

Lulu finds a scorecard with every third box punched, and the Secret Snack Club punches every third box to cast a vote. Her top bun is 'this was a club ballot, not doodle paper.' The secret sauce: the holes were not made later by something random, like Mr. Whiskers chewing it.

Step 2 · The kid story

The Punched Scorecard

Lulu finds an old scorecard under the reading rug. Every third box has a neat little hole in it. She taps her clipboard. "The Secret Snack Club votes by punching every third box. That is their rule. So this is not scrap paper. This is a club ballot!" Marcus gasps. "Case closed, Detective Lulu." Priya sets down her juice box. "Wait. The rug is where Mr. Whiskers naps. And the class hole puncher fell back there last week and got stepped on a bunch. What if the holes showed up later, by accident?" Lulu frowns, then nods slowly. "Then my ballot idea needs one more thing. The holes have to come from a person punching on purpose, not from something that happened to the card after it landed here." She writes it down twice, just to be safe.

Step 3 · Try the model question

Lulu: This scorecard has a hole in every third box. The Secret Snack Club casts votes by punching every third box. So this card is a club ballot, not scrap paper.

Lulu's conclusion relies on which assumption?

Step 4 · The courtroom tale

The Case of the Knotted Kite String

A prosecutor holds up a kite string tied in three tight knots. "Your Honor, the Kite Club marks a winning kite with exactly three knots. This string has three knots. So it came from a winning kite." Mr. Whitfield rises. "May I ask where it was found?" "In a tree," the prosecutor admits. "In a windy tree," says Mr. Whitfield. "Strings flapping in branches tangle into knots all by themselves. Your case needs those knots to have been tied on purpose, not twisted in by the wind afterward." The judge nods. "Pull that plank and the whole argument drops. Bring me proof the knots were deliberate."

Step 5 · Work the real question

Open PrepTest 136, Section 2, Question 2 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the clue in the evidence and the custom it seems to match. Then find the conclusion that the item belongs to that custom. Ask what else could have produced the same clue, especially something that happened later. Test each choice with Pull the Plank: negate it and see if the conclusion breaks. The right one blocks an alternate cause. Prefer the modest choice over one that reaches farther than the argument needs.