Logical Reasoning · Necessary Assumption

PrepTest 152 · Section 2 · Question 25

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 evidence is about one buyer's demand, but the conclusion is about how easy something is to sell in general, so the argument needs that one kind of demand to matter a lot.

The basic logic

Spot the Scope Shift: the patty covers why one kind of buyer passes on older items; the top bun says older items are harder to sell overall. The secret sauce links them: how easy the older items are to sell depends mostly on that kind of demand. Pull the Plank to check.

Tiny words that decide it

“the more”
“because”
“generally”
“tend”

Playground logic

Lulu notices the swap table takes newer stickers and passes on old ones, since kids want to re-trade new ones. Marcus concludes newer stickers are easier to trade overall. That only holds if trading old stickers depends mostly on that re-trade demand.

Step 2 · The kid story

The Sticker Swap Table

Ms. Rivera set up a sticker swap table. Marcus made a speech. "Everybody knows: when kids want a thing more, it gets easier to trade. The swap table always takes stickers less than a year old, because kids snap them right up again. But nobody wants old stickers to re-trade, so the swap table usually passes on those. So newer stickers are just easier to trade, period." Priya sipped her juice box. "Hold on. You only talked about the swap table. What about Grandpa? He collects old stickers. And Owen trades his old ones to his cousin." Marcus scratched his head. Lulu wrote: Marcus needs old stickers to be traded mostly based on whether kids want to re-trade them. If Grandpa's collection is the real market, his claim falls apart. Marcus quietly checked how many stickers Grandpa owned.

Step 3 · Try the model question

Marcus: When kids want a thing more, it gets easier to trade. The swap table always takes stickers less than a year old, since kids quickly re-trade them. But kids rarely want old stickers to re-trade, so the swap table tends to pass on those. Therefore, newer stickers usually trade more easily than old ones.

Which one of the following must Marcus assume for his argument to work?

Step 4 · The courtroom tale

The Case of the Old Comic Books

The comic shop's lawyer stood. "Your Honor, when more people want a thing, it sells more easily. The used bookstore buys every comic less than five years old, because readers grab them fast. Older comics have few readers, so the store usually passes. Therefore, older comics are harder to sell." Mr. Whitfield hooked his thumbs in his suspenders. "Counsel only told us about one store. Collectors pay fortunes for old comics at conventions." The judge frowned. "So your argument needs the selling of old comics to depend mostly on what readers at that store want." The lawyer coughed. "May I have a recess?"

Step 5 · Work the real question

Open PrepTest 152, Section 2, Question 25 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the narrow evidence (one kind of buyer and why it passes on older items) and the broad top bun (older items are harder to sell in general). The gap is the link between them. Look for the choice that says the selling of the older items depends largely on that narrow kind of demand. Use Pull the Plank: negate it and see if the conclusion falls. Avoid Megaphone choices that say 'not any' or 'all'.