PrepTest 151 · Section 3 · Question 25 (Parallel Reasoning)

Step 1 · Pre-Question Guidance · read this first

Question type

Parallel Reasoning

The one idea it tests

Narrow the suspects to two who could do it, rule one out because only the other had a reason, and name the one left.

The basic logic

X-Ray the skeleton: only two people had the chance; one had a motive and one had none; so it must be the one with the motive. Match chance, motive, and a definite conclusion. Watch for answers that swap motive with fear, past habits, credit, or skill.

Tiny words that decide it

“only”
“no reason”
“must have been”

Playground logic

Only Tommy and Kevin were near the cookie tin; Tommy wanted the cookies and Kevin had no reason to take them; so it was Tommy. The skeleton is: two with access, one with motive, so the one with motive.

Step 2 · The kid story

The Empty Cookie Tin

Aunt Rosa's cookie tin was empty. Lulu got out her clipboard. "Who was in the kitchen this afternoon?" Only two people: Tommy and Kevin. Nobody else came in. "Tommy loves these cookies," Lulu said. "He has been staring at that tin all week." "And Kevin?" asked Priya. "Kevin only eats pineapple pizza," said Lulu. "He had no reason to take cookies." Marcus spread his arms. "Then it must have been Tommy!" Tommy, with crumbs on his shirt, said nothing. Lulu wrote: Two had the chance. Only one had a reason. So that one did it. Priya nodded. "Same shape as any good mystery. Chance, then motive, then the answer."

Step 3 · Try the model question

Only Tommy and Kevin were in the kitchen when the cookies vanished. Tommy loves those cookies, but Kevin had no reason to take them. So it must have been Tommy who took the cookies.

The pattern of reasoning in which one of the following is most like that above?

Step 4 · The courtroom tale

The Missing Trophy

The bowling league trophy disappeared from the clubhouse. "Your Honor," said Mr. Whitfield, "the logbook shows only two people had the clubhouse key that night: the league treasurer and the janitor." He paced. "The treasurer lost the final match and swore he would get that trophy no matter what. The janitor? He doesn't even bowl. He had no reason at all." The judge folded her hands. "Only two had the chance, and only one had a reason." "So the treasurer it must be," said Mr. Whitfield. The treasurer coughed, and a bowling pin rolled out from under his coat.

Step 5 · Work the real question

Open PrepTest 151, Section 3, Question 25 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Write the skeleton of the stimulus first: two people were the only ones able, one had a reason and the other had none, so it must be the first. Then X-Ray each choice. Check that the suspects are narrowed to two by opportunity, that the deciding fact is motive versus no motive, and that the conclusion is definite. Eliminate choices where the deciding fact is a denial, a fear, a missing claim of credit, or a prediction.