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Logical Reasoning · Parallel Reasoning

PrepTest 152 · Section 2 · Question 19

Phase 1 (your first ~400 questions): read the guidance, then answer. No clock.

Step 1 · Pre-Question Guidance · read this first

Question type
Parallel Reasoning
The one idea it tests
Match the skeleton: some of group one have a trait, nothing in group two has that trait, so group one is not entirely group two.
The basic logic
X-Ray the argument into letters: Some A are B. No C is B. So not all A are C. Then X-Ray each choice. The order of the sentences may be shuffled, so match the logic, not the sentence order.
Tiny words that decide it
  • “some”
  • “no”
  • “not all”
  • “therefore”

Playground logic

Kevin's playlist has some dinosaur songs. Lulu says no long song is a dinosaur song. So not every song on the playlist is long. Some A are B, no C is B, so not all A are C.

Step 2 · The kid story

Kevin's Playlist

Kevin plugged his music player into the classroom speaker. "Some of my songs are dinosaur songs," he announced. "There's one about a stegosaurus who loves pineapple pizza." Lulu flipped to a clean page on her clipboard. "Ms. Rivera said our song rule is simple: no song longer than five minutes is a dinosaur song. The dinosaur songs are all short and silly." Owen grinned. "So Kevin's playlist can't be all long songs. At least one song on there is short." Kevin blinked. "How do you know? You haven't heard them yet!" "Easy," said Priya. "Some of your songs are dinosaur songs. No long song is a dinosaur song. So the dinosaur ones can't be long, which means not every song is long." Kevin pressed play. The stegosaurus song lasted forty seconds. Everybody clapped.

Step 3 · Try the model question

Some of the songs on Kevin's playlist are dinosaur songs. No song longer than five minutes is a dinosaur song. Therefore, not every song on Kevin's playlist is longer than five minutes.

Which choice uses the same shape of reasoning as the argument about Kevin's playlist?

Choices

Step 4 · The courtroom tale

The Case of the Missing Tuba

A judge studied a list of the town's marching bands. "Counsel, your point?" Mr. Whitfield bowed. "Your Honor, some of the bands on this list march in the winter parade. And no band with a tuba section marches in the winter parade, since tubas freeze. Therefore, not every band on this list has a tuba section." The opposing lawyer jumped up. "You never checked the bands one by one!" "I didn't need to," said Mr. Whitfield. "Some on the list have the parade trait. No tuba band has it. So the list cannot be all tuba bands." The judge nodded. "The logic is as tight as a frozen valve."

Step 5 · Work the real question

Open PrepTest 152, Section 2, Question 19 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Turn the stimulus into letters: some A are B, no C is B, so not all A are C. Do the same for each choice, writing its letters down. Remember the choices may say the premises in a different order, or phrase 'not all A are C' as 'some A are not C'. Keep the choice whose letters line up. Toss any choice with two 'some' premises or two 'no' premises.