Logical Reasoning · Inference

PrepTest 113 · Section 3 · Question 15

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

Step 1 · Pre-Question Guidance · read this first

Question type

Inference (Cannot Be True)

The one idea it tests

A share is a part divided by a whole; if the part holds steady and the share drops, the whole must have grown.

The basic logic

Track three numbers: one player's count, everyone else's count, and the total. If the player's count stays flat while the player's share falls, the total rose, so everyone else rose too. The answer that says the rest went down is impossible.

Tiny words that decide it

“CANNOT”
“share”
“constant”

Playground logic

Tommy's weekly sticker count stayed flat after the new rule, but his share of all stickers dropped a lot. A smaller slice from the same-sized piece means the whole pie grew, so the other kids must have gotten more stickers, not fewer.

Step 2 · The kid story

The Sticker Chart Math

Ms. Rivera gives out the same total number of gold stickers every week. For several weeks, Tommy's weekly stickers doubled, so his share of the class total went way up. He was very proud. Then Ms. Rivera added a new rule: stickers for helping clean the fish tank. After that, Tommy still got exactly as many stickers each week as before. But his share of all the stickers dropped a lot. "How?" Tommy wailed. Lulu pulled out her clipboard and did the math. "Your stickers stayed the same. Your slice got smaller. That only works if the whole pile got bigger. So the other kids must be getting more stickers now." Tommy sighed. "Biscuit probably got a sticker for licking the fish tank."

Step 3 · Try the model question

For several weeks, the class received the same total of stickers each week, while Tommy's weekly count doubled and his share rose. Then a new rule began. Afterward, Tommy's share fell sharply even though his weekly count stayed at its new level.

If all of this is accurate, which one of the following is impossible?

Step 4 · The courtroom tale

The Case of the Shrinking Slice

A farm stand sued a rival, claiming the rival's sales of apples had dropped. Mr. Whitfield called the market clerk. "Did my client sell the same number of apples each week after the new parking lot opened?" "Yes, exactly the same." "And did my client's share of all apples sold at the market fall?" "Sharply." Mr. Whitfield turned to the judge. "Your Honor, same apples, smaller share. That means the total grew, and since my client stayed flat, everyone else sold more. The claim that the other stands sold fewer is not just unproven. It is impossible." The judge closed the file.

Step 5 · Work the real question

Open PrepTest 113, Section 3, Question 15 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Write down the three numbers: one party's amount, everyone else's amount, and the total. Note which stayed constant and which share moved, period by period. Use the rule that share equals part divided by total to see what must have happened to the total and to the others in the later period. Then pick the answer that contradicts that. Answers about causes, profits or future events usually could be true.