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LSAT must be true questions give you facts rather than an argument and ask what follows with certainty. Recognize them from if the statements above are true, which one of the following must also be true. Solve them by combining statements mechanically and refusing anything that requires an outside assumption.
Recognition is the cheapest point on the section. Every must be true question announces itself in the stem, and the stems recycle a small number of formulations. Learn them and you stop spending seconds deciding what you are being asked.
Stem wordingWhat it tells youIf the statements above are true, which one of the following must also be true?The canonical stem. Must is absolute.Which one of the following can be properly inferred from the statements above?Properly inferred means with certainty, not plausibly.The statements above, if true, most strongly support which one of the following?A softer cousin. Here the standard drops to best supported, so a strong-but-not-certain answer can win.If the information above is correct, which one of the following cannot be true?The negative form. You are looking for the choice that contradicts the set.
Read the stem before the stimulus. Knowing you are hunting inference changes what you notice on the first read, and reading the stimulus cold means reading it twice.
Three steps, in this order. The order is the method, because the most common way to lose this question type is to read the answer choices before you have decided what you are looking for.
StepWhat it means in practiceNotice that there is no conclusion to findThese are fact sets, not arguments. Time spent hunting for a conclusion is time wasted, and treating a fact set like an argument is the most common structural error on the type.Combine only where the statements genuinely overlapTwo conditionals chain when the necessary condition of one is the sufficient condition of another. Write the contrapositives. Most correct answers on this type are a chain or a contrapositive, and most wrong answers are a chain that does not connect.Hold the standard at must, not probablyIf you can imagine any consistent world where the statements hold and the choice fails, the choice is wrong. Reasonableness is not the test. Certainty is.
The stimulus and answer choices below were written for this page. They are not taken, adapted or paraphrased from any real LSAT question, because reproducing licensed test content is not something we do. The style is the target; the content is ours.
Stimulus.
Every apartment in the Fairlawn building that has a balcony also has a south-facing window. No apartment on the ground floor of the Fairlawn building has a south-facing window. Some apartments on the ground floor have been renovated in the past year.
Question. If the statements above are true, which one of the following must also be true?
(A) No apartment on the ground floor of the Fairlawn building has a balcony
(B) Every apartment in the Fairlawn building with a south-facing window has a balcony
(C) Some renovated apartments in the Fairlawn building have balconies
(D) Every apartment above the ground floor of the Fairlawn building has a south-facing window
(E) No apartment renovated in the past year has a south-facing window
The answer is (A).
Write the first statement as balcony leads to south-facing window. Its contrapositive is no south-facing window leads to no balcony.
The second statement puts every ground-floor apartment in the no south-facing window category, so every ground-floor apartment lands in the no balcony category. That chain is airtight, and the renovation statement is there to distract.
Reviewing the four wrong answers is worth more than confirming the right one. Each was engineered to catch a specific misreading, and naming that misreading is what stops it recurring.
ChoiceWhy it failsBThe reversal. Balcony guarantees a south-facing window; a south-facing window guarantees nothing.CThe renovated apartments named are on the ground floor, which we just showed have no balconies. Nothing establishes balconies among any other renovated units.DNothing is said about apartments above the ground floor at all. Only the ground floor was ruled out.ERenovation was mentioned only for ground-floor apartments. Other apartments may have been renovated and may have south-facing windows.
Across must be true questions, the wrong answers fall into recurring shapes. Once you can name the shape you can eliminate on sight instead of arguing with each choice on its merits.
TrapHow it worksThe reversalSwaps sufficient and necessary. The most reliably tempting wrong answer on the type.The negation without contrapositionNegates both terms but leaves the arrow pointing the same way, which is not a valid move.The plausible extraA statement that would probably be true in the real building and is not entailed by the words on the page.The unwarranted someTurns two overlapping groups into a claimed intersection the statements never guarantee.
One question people always ask about must be true questions is how many appear per test. There is no honest answer to give. LSAC does not publish how many questions of each type appear on a given test, and no honest page can give you a percentage without inventing it.
What is published is the scored structure: the LSAT is two scored Logical Reasoning sections and one scored Reading Comprehension section, four 35-minute sections in total including one unscored variable section, with a 10-minute intermission after section two, per LSAC's own test specifications (https://www.lsac.org/lsat/register-lsat/accommodations/specifications-lsat-and-lsat-argumentative-writing). Two of the three scored sections are Logical Reasoning, so LR carries roughly two thirds of your scored questions.
That ratio is worth planning around. A per-type count is not, because nobody outside LSAC has one.
That matters practically, because study plans built on invented percentages allocate your weeks wrong. If you read that must be true questions are eleven percent of the test, ask where the number came from. It came from somebody counting a handful of released tests and rounding, which is not the same thing as a published specification.
Plan on the structure instead. Two of your three scored sections are Logical Reasoning, must be true questions appear in both, and no single LR type is rare enough to skip or common enough to carry your score by itself.
Drilling must be true questions in a block is efficient for learning the pattern and misleading about whether you have learned it. Blocked practice lets you know the question type before you read the stimulus, which is exactly the cue the real test removes.
The size of that gap is measured. In a classroom study of 787 students across 54 classrooms, interleaved practice produced 61 percent correct against 38 percent for blocked practice at a 33-day delay, an effect of d = 0.83, per Rohrer, Dedrick and Hartwig (2019), Journal of Educational Psychology (https://gwern.net/doc/psychology/spaced-repetition/2019-rohrer.pdf). Blocked practice felt better and tested worse.
The same reversal shows up in how students judge their own learning. Kornell and Bjork (2008), Psychological Science (https://gwern.net/doc/psychology/spaced-repetition/2008-kornell.pdf) found 78 percent of students judged massed study as good as or better than spaced study while 78 percent actually performed better spaced. Your sense that a drill block is working is not evidence that it is.
So use blocks to build the recognition, then stop. Once you can name a must be true question from the stem without thinking, the questions belong back in mixed sets where you have to identify the type yourself, because identifying it is half the skill.
Review is where the points are, and review is not reading the explanation for the answer you missed. The intervention research is blunt about this: across 28 studies and more than 16,000 participants, test prep as a category produced an overall effect of g = .26, and practice tests on their own produced g = .19 at p = .233, which is not statistically significant, per Hao and colleagues (2025), Review of Educational Research (https://journals.sagepub.com/doi/10.3102/00346543251360775). Taking questions is not the active ingredient.
What did work in that same Hao and colleagues analysis was structured practice on the reasoning: workbooks at g = .40 and explicitly teaching test-taking skills at g = .35. And there was no dose response at all, with neither contact hours at p = .489 nor program length in weeks at p = .314 predicting outcomes.
More hours is not the lever. Better review is.
Concretely, for every must be true question you get wrong, write three lines before you look at any explanation: what you thought the inference was, what it actually was, and the exact word in the stimulus that would have told you. The third line is the one that transfers.
Then leave the question alone for at least a day before you revisit it. Testing yourself beats restudying at g = 0.50 across 61 studies, the advantage rises to g = 0.69 when the delay is a day or more against g = 0.41 under a day, and feedback roughly doubles the effect at g = 0.73 with against g = 0.39 without, per Rowland (2014), Psychological Bulletin (https://pubmed.ncbi.nlm.nih.gov/25150680/).
Every LSAC figure on this page was taken from LSAC's own pages and last checked on July 26, 2026. Prices, dates and policies move without notice, so the source link sits next to each number rather than in a bibliography at the bottom.
Where LSAC has not published something, this page says so in those words rather than filling the hole with a plausible number. That is the difference between a gap and a guess, and only one of them is safe to plan around.
If the statements above are true, followed by must also be true or can be properly inferred. Watch for the softer most strongly support variant, which lowers the bar.
Diagram the conditionals and their contrapositives, chain only where terms genuinely match, and reject any choice that needs a fact from outside the stimulus.
LSAC publishes no per-type breakdown. The published structure is two scored Logical Reasoning sections and one Reading Comprehension section, per LSAC's own specifications.
Must be true demands certainty. Most strongly supported accepts the best-supported choice even if it is not entailed, so a reasonable inference can win there and would lose here.
Shorthand arrows and contrapositives are enough. The value is in externalizing the relations so you stop testing them against intuition, which is where the reversal trap catches people.
Written by Ali, Georgetown Law, founder of Lovare Institut.
August 5, 2026
August 5, 2026