Logical Reasoning · Principle

PrepTest 133 · 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

Principle (identify the principle)

The one idea it tests

When an argument gives two contrasting cases with matching advice, the principle is the rule that ties how much you invest to the feature that differs between them.

The basic logic

Spot what varies between the two cases (how long each item stays useful) and how the advice changes (spend more vs. spend less). The principle links them: spending should scale with how long you'll use the thing.

Tiny words that decide it

“so”
“the longer”
“roughly”

Playground logic

Grandpa's patty has two cases: a lunchbox you'll use for years and party streamers you'll use for one afternoon. His advice changes with how long each one lasts, and the secret sauce is a rule: match what you spend to how long you'll use it.

Step 2 · The kid story

Grandpa's Shopping Rule

Grandpa took Tommy and Lulu to the store before school started. Tommy grabbed the cheapest lunchbox he could find. "Put that back," said Grandpa. "You'll carry a lunchbox every day for three or four years. Spend a bit more and get a sturdy one." Then Lulu reached for fancy glittery party streamers for her friend's birthday. Grandpa shook his head. "Those go up for one afternoon and then into the trash. Get the cheapest ones." Tommy frowned. "So sometimes cheap is good and sometimes cheap is bad?" Lulu checked her clipboard. "No, there's one rule. The longer you'll use it, the more it makes sense to spend." Grandpa winked. "That's my girl."

Step 3 · Try the model question

Grandpa: A lunchbox will be used every school day for years, so it is worth paying more for a sturdy one. Birthday streamers will be thrown away after one party, so you should spend as little on them as you can.

Grandpa's advice is best explained by which rule?

Step 4 · The courtroom tale

The Bicycle Budget Hearing

A school board was sued over its purchases. It spent a lot on sturdy bike racks but very little on paper sign-up sheets. "That's inconsistent!" cried the plaintiff's lawyer. "Either they care about quality or they don't." Mr. Whitfield stood up. "Your Honor, the bike racks will be bolted to the ground for twenty years. The sign-up sheets get tossed every Friday. The board follows one rule: the longer something will be used, the more it's worth spending on it." The judge nodded. "Not inconsistent at all. Two different cases, one rule." Case dismissed.

Step 5 · Work the real question

Open PrepTest 133, Section 2, Question 7 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

List the two cases and the advice given for each. Ask which feature differs between them and drives the change in advice. State the rule in your own words before reading the choices. The right answer links the amount invested to that feature, and it must fit both cases at once. Eliminate rules that fit only one case, that the advice in one case would break, or that rest on a feature the argument never uses.