Logical Reasoning · Inference (Most Strongly Supported)

PrepTest 116 · Section 3 · Question 24

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

Step 1 · Pre-Question Guidance · read this first

Question type

Inference (Most Strongly Supported)

The one idea it tests

When one group always keeps something, anything that lacks it cannot be in that group (the contrapositive).

The basic logic

The passage describes several groups and explains which ones keep a certain feature and which lose it. One group can never lose it. Turn that around: anything without the feature is not in that group. Beware answers that say everything without the feature belongs to one specific other group, since the passage never says the groups are the only options.

Tiny words that decide it

“cannot”
“no”
“any”
“because”

Playground logic

The patties: big jars keep cookies because no one reaches the back, small tins get emptied, and the stuck-lid jar can never be eaten from. The Lunchbox Rule lets us flip one fact: an empty jar cannot be the stuck-lid jar. Claiming more than that, like 'every empty jar is a tin', is a Megaphone.

Step 2 · The kid story

Aunt Rosa's Three Jars

Aunt Rosa keeps three kinds of cookie jars. Big glass jars always have cookies left on Friday, because nobody can reach the back of them. Small tin jars are always empty by Friday, because every cookie is easy to grab. And then there is the medium jar with the stuck lid. Nobody can open it, not even Grandpa, so its cookies can never be eaten. On Friday, Tommy finds an empty jar on the counter. 'Which one is it?' he asks. Lulu checks her clipboard. 'I can't say for sure. But I know one thing. It is not the stuck-lid jar, because that jar can never lose its cookies.' Priya agrees. 'Empty means not stuck. That is all the facts let us say.'

Step 3 · Try the model question

Aunt Rosa's big glass jars always still have cookies by Friday, because no one can reach the back. Her small tin jars are always empty by Friday, because every cookie is easy to grab. Her medium jar has a stuck lid that no one can open, so its cookies can never be eaten.

Which choice gets the strongest backing from the facts above?

Step 4 · The courtroom tale

The Jammed Locker Mystery

In a fictional gym, three kinds of lockers line the wall. Large lockers are rarely emptied. Small ones are emptied every night. And the old blue lockers are jammed shut forever, so nothing inside can ever be taken out. A gym bag goes missing from an emptied locker. The prosecutor points at a man who rents a blue locker. Mr. Whitfield raises a finger. 'Your Honor, the missing bag came from a locker that was emptied. A jammed blue locker can never be emptied. So the bag was not in a blue locker, and my client's locker has nothing to do with it.' The judge nods. 'Emptied means not jammed. That much is certain.'

Step 5 · Work the real question

Open PrepTest 116, Section 3, Question 24 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

List each group the passage describes and what it says happens to the feature in that group. Look for the group that can never lose the feature, and write its contrapositive: lacks the feature, so not in that group. Prefer the answer that is just that flip. Be suspicious of answers claiming that anything with or without the feature must belong to one particular other group; the passage never says its groups are the only ones.