AP Precalculus has four units and the exam assesses three of them. Unit 4, Functions Involving Parameters, Vectors, and Matrices, is marked "Not assessed on the AP Exam" in College Board's own course and exam description.

That is the most expensive thing to not know about this exam, and it is easy to miss, because a precalculus textbook will happily teach you parametric equations, conic sections and matrix inverses.

Three units carry the exam

College Board's reason is about college credit rather than difficulty. Units 1 to 3, it says, cover the content "in which colleges and universities typically expect students to be proficient, in order to qualify for college credit and/or placement."

• Unit 1: Polynomial and Rational Functions
• Unit 2: Exponential and Logarithmic Functions
• Unit 3: Trigonometric and Polar Functions
• Unit 4: Functions Involving Parameters, Vectors, and Matrices, not assessed

Unit 3 alone is 30 to 35% of the multiple-choice section.

If your teacher covers Unit 4, that is a defensible choice and the material matters for later courses. It is not exam preparation, and hours spent there in May are hours not spent on polar functions.

Some trigonometric identities are assessed and some are not

This is narrower than the unit exclusion and easier to waste a week on. The course description is specific about which identities appear.

Assessed: Pythagorean identities, and the sum, difference and double-angle identities for sine and cosine.

Not assessed: half-angle identities, tangent sum and difference identities, and other identities not listed.

So the identity sheet in the back of a textbook is wider than the exam. If you are drilling half-angle manipulations for AP Precalculus specifically, you are drilling something that will not be asked.

One interval distinction is explicitly ruled out

The course description carries a formal exclusion statement, and it is unusually precise. Discriminating between open and closed intervals, as it relates to intervals where a function is increasing or decreasing, is outside the scope of the course and exam.

You still have to read a graph and say where the behavior changes. What you will not be assessed on is whether the endpoint belongs inside that interval.

This matters mainly as a filter on practice material. A question whose four answer choices differ only in square brackets versus round ones, on an increasing or decreasing interval, is testing something College Board has said it does not test.

Endpoints still matter elsewhere. Domain restrictions and average rates of change over a closed interval both need precise notation. The exclusion is specific to the increasing and decreasing case.

The May 2027 clock, and the one-line test for your practice material

College Board has also updated the question counts and the section timing, effective with the May 2027 exam. The current structure:

Total testing time is 2 hours 55 minutes. Multiple choice is 62.5% of the score.

That gives about 2 minutes 14 seconds per question in the no-calculator block and about 3 minutes 5 seconds in the calculator block. Averages are planning tools and not limits; some questions deserve longer.

The useful test: if your practice material says anything other than 29 questions in 65 minutes for the no-calculator section, it predates this change. That is a faster check than reading a publisher's copyright page, and it tells you what the material can and cannot be used for.

College Board publishes the old figures too, in a separate clarifications and corrections document rather than on the exam page, which is why the comparison is harder to find than the change itself:

• Part A went from 28 questions in 80 minutes to 29 in 65.
• Part B went from 12 questions to 13, with its 40 minutes unchanged.
• Both free-response parts went from 30 minutes to 35.

So the no-calculator block is where the pressure moved. It gained a question and lost a quarter of an hour, taking the average from about 2 minutes 51 seconds a question down to about 2 minutes 14. The exam as a whole lost five minutes, which is the least interesting number in this post.

What the free-response section asks

Four questions, two per part, and they have fixed subjects rather than being interchangeable:

1. Function Concepts, with a calculator.
2. Modeling a Non-Periodic Context, with a calculator. It currently has three parts: build a function model from the given information, calculate and apply average rates of change with their units, then answer a question about the model.
3. Modeling a Periodic Context, no calculator.
4. Symbolic Manipulations, no calculator.

Both Questions 1 and 2 changed, and the clarifications document says exactly how. In Question 2, Part B (iii) was removed and Part C was modified to broaden the question, with the scoring guidelines updated to match. Question 1 has a minor modification to Part C (i) with no change to its scoring.

So an older Question 2 has a subpart the current one does not. It is still worth working for the modeling itself. It is not a rehearsal of the sequence you will meet.

How to audit your own material in ten minutes

1. Count the no-calculator multiple choice. Anything other than 29 in 65 minutes is pre-2027.
2. Look for Unit 4 content. Parametric equations, vectors, matrices, conic sections. Skip it for exam purposes.
3. Check the identity work. Half-angle and tangent sum questions are not exam-aligned.
4. Scan increasing and decreasing interval questions. If the options differ only by bracket type, the question is testing an excluded distinction.
5. Check Question 2 for a removed subpart. If its Part B has a third piece, the question predates the change.

Older material is not worthless. It teaches the functions, and the mathematics does not expire. What expires is the claim that working through it simulates the exam, which is a separate question from whether the answers are right. We wrote about that distinction more generally in why practice questions expire even when their answers are still correct.

Write the four section limits at the top of your next full session: 65, 40, 35, 35. Then check that your material actually fits them.