Logical Reasoning · Inference

PrepTest 119 · 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

Inference / Must Be True

The one idea it tests

Chain a requirement to a 'none has it' fact: if the second kind of behavior needs something no member has, every member is stuck with the first kind.

The basic logic

There are two kinds of behavior. The second kind needs a big amount of something. No member of a certain group has reached that amount. So no member can do the second kind, which leaves only the first kind. Stay inside the lunchbox: say nothing about groups that do have the big amount.

Tiny words that decide it

“must”
“no”
“yet”
“only”

Playground logic

Lego builds come in two kinds: follow-the-instructions or invent-your-own. Invent-your-own needs at least 500 bricks, and no kid in Lulu's class has a bucket that big yet. So every build in Lulu's class is a follow-the-instructions build.

Step 2 · The kid story

The Brick Bucket Rule

Ms. Rivera explained Lego builds to the second graders. "There are two kinds. Follow-the-instructions builds can look super fancy, like a castle with a drawbridge, but you just copy the booklet, and you need far fewer bricks. Invent-your-own builds need imagination and a giant pile: at least 500 bricks to choose from." Lulu raised her hand. "Nobody in our class has 500 bricks yet. I checked." She held up her clipboard as proof. Marcus, visiting from fifth grade, jumped in. "So every kid with a big bucket invents their own stuff!" Priya shook her head. "Nope. Big buckets are needed, not enough. Here's what we actually know: every build in Lulu's class is a follow-the-instructions build. That's it." Mr. Whiskers knocked over the castle.

Step 3 · Try the model question

Lego builds are either follow-the-instructions builds or invent-your-own builds. Instruction builds can be fancy but need fewer bricks. An invent-your-own build requires a bucket of at least 500 bricks, and no second grader in Lulu's class has a bucket that large yet.

Which one of these must be true if everything said is true?

Step 4 · The courtroom tale

The Robot Contest Ruling

A robot contest had two kinds of entries: kit robots built from a manual, and original robots designed from scratch. Rules said original robots require a workshop with a lathe. A parent sued, claiming the junior league was robbed of an originality prize. Mr. Whitfield stood. "Your Honor, no junior team has a lathe yet. The records are clear." Judge Patel nodded. "Then every junior entry was a kit robot. No originality prize was possible." The parent's lawyer tried one more angle: "So every team with a lathe built an original!" The judge shook her head. "A lathe is required, counsel, not a guarantee. I rule only on what follows."

Step 5 · Work the real question

Open PrepTest 119, Section 2, Question 7 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Spot the two categories of behavior and treat them as the only options. Turn the size claim into a requirement for the second category. Add the fact that no member of the named group meets it. Predict: that group's behavior is entirely the first category. Reject choices that flip the requirement into a guarantee for larger groups, or that make claims about everyone above or below the size line.