Logical Reasoning · Necessary Assumption

PrepTest 152 · Section 2 · Question 23

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

To show something was passed on to others, the later group must include some who were not in the first group.

The basic logic

The top bun has two parts. Check whether the patty supports both. If the evidence could all come from the original group, the 'passed on' part has no support. The secret sauce is that some later members were newcomers. Pull the Plank: if none were newcomers, the second part collapses.

Tiny words that decide it

“even”
“pass on”
“some”
“not”

Playground logic

Ms. Rivera taught a secret handshake to five kids, and months later kids at school were doing it. Priya's top bun says the handshake spread to others. That only works if some of the June handshakers were not in the first five.

Step 2 · The kid story

The Secret Handshake

In September, Ms. Rivera taught a silly secret handshake to five kids: two claps, a wiggle, and a thumb bump. In June, Nadia spotted kids at the drinking fountain doing the exact same handshake. "It spread!" she said. "Kids can learn a handshake and teach it to other kids!" Marcus nodded hard. "Case closed." Priya sipped her juice box. "Wait. Who did you see doing it?" Nadia thought. "Some kids." "What if they were the same five kids from September?" said Priya. "Then nothing spread. They just remembered." Lulu wrote it down: For 'it spread' to work, at least some of the June handshakers have to be new kids. Nadia ran back to the fountain to check names. Two of the handshakers were first graders. "It spread!" she shouted again.

Step 3 · Try the model question

Nadia: Kids can learn a handshake and even teach it to other kids. In September, Ms. Rivera taught a special handshake to five students. In June, kids near that classroom were seen doing the same handshake.

Nadia's argument requires assuming which one of the following?

Step 4 · The courtroom tale

The Case of the Knitting Stitch

The craft guild's lawyer stood. "Your Honor, a fancy stitch can be learned and passed along. Ten years ago, the guild taught it to a class of twelve. This spring, scarves with that stitch filled the town fair." Mr. Whitfield raised a hand. "Who knitted those scarves, counsel?" "Knitters in town." "If every one of them came from that original class of twelve," said Mr. Whitfield, "then nothing was passed along. Those twelve simply kept knitting." The judge nodded slowly. "So your claim needs at least some knitters who learned it from someone else." The guild's lawyer sighed and pulled out a fresh sign-in sheet.

Step 5 · Work the real question

Open PrepTest 152, Section 2, Question 23 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Split the conclusion into its parts and ask which part the evidence has not covered yet. When a claim says something spread or was passed on, check whether the later group might be the same as the first. Then use Pull the Plank on each choice: negate it and see if the argument breaks. Keep the one whose denial wrecks the 'passed on' part. Watch for Megaphone choices that use 'always' or 'most'.