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Logical Reasoning · Parallel Flaw

PrepTest 123 · 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
Parallel Flaw
The one idea it tests
Mixing two extremes is assumed to produce a middle, and the right answer makes the same exact leap.
The basic logic
X-Ray the flaw: group one is all very high, group two is all very low, the thing is a blend of the two, so it must be medium. Find the choice with that skeleton and that mistake.
Tiny words that decide it
  • “all”
  • “each”
  • “therefore”
  • “moderate”

Playground logic

Frankie says every sticker from one pack is super shiny and every sticker from the other is totally flat, so a sticker made by gluing one of each together must be medium shiny. That is a jump: the blend could look just like one parent. The patty is about the two extremes; the top bun quietly assumes blends land in the middle.

Step 2 · The kid story

Frankie's Half-Shiny Theory

Frankie dumped two sticker packs on the desk. 'Every sparkle sticker is super shiny. Every chalk sticker is totally flat.' Then he glued one of each together, back to back, and held up his creation. 'So this combo sticker is medium shiny. Science!' Sharon squinted. 'Says who? Maybe the sparkle side wins and it is just as shiny. Maybe the chalk side wins and it is flat. Mixing a super thing and a zero thing does not have to give you a middle thing.' Lulu wrote on her clipboard: Extreme plus extreme does not equal medium. Frankie frowned. 'Then what is it?' 'Look at it,' said Sharon. 'Do not do math on it.' Frankie tilted the sticker in the light. Only one side sparkled.

Step 3 · Try the model question

Every sparkle sticker is extremely shiny. Every chalk sticker is completely flat. Frankie's combo sticker is made from one sparkle sticker and one chalk sticker. So Frankie's combo sticker is medium shiny.

Which choice contains a mistake in reasoning most like Frankie's?

Choices

Step 4 · The courtroom tale

The Lukewarm Lemonade Case

A lawyer named Ms. Pell rose. 'Your Honor, the giant ice cubes from Freezer One are freezing cold. The kettle water from Stand Two is boiling hot. My client's drink is a blend of both. So it is pleasantly lukewarm, and nobody could have been surprised by it.' Mr. Whitfield stood, tugging his suspenders. 'Your Honor, a blend of two extremes does not have to land in the middle. One huge cube in a thimble of hot water? Still freezing. One cube in a pot? Still scalding.' The judge nodded. 'Mixing is not averaging, Ms. Pell. Did anyone taste it?'

Step 5 · Work the real question

Open PrepTest 123, Section 2, Question 2 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Strip the argument down to letters: all of type one has an extreme trait, all of type two has the opposite extreme, this thing blends both, so it is medium. Name the flaw: blends need not average out. Then X-Ray each choice for the same three-part setup and the same middle-ground conclusion. Cross out any choice whose conclusion is actually valid or whose premises use 'some' instead of 'all.'