IC / Intermediate
Intermediate Counting and Probability
Probability Lab
Develop counting arguments using distributions, recurrences, conditioning and graphs.
Preparation: Combinations, elementary probability, binomial coefficients and algebra.
Current coverage: 12 core stages including inclusion–exclusion, Catalan counts, Bayes and graph invariants.
LEVEL 1 · DIFFICULTY 1/5 within this course
Sets and Distributions
Handle overlaps and constrained allocations.
Explore 3 knowledge islands
Choose an island to read its lesson.
3 stages · 24 library problems · 108 checked variations · 2 × 6 assessment questions
Read the lessons →LEVEL 2 · DIFFICULTY 2/5 within this course
Exclusion, Expectation and Recurrences
Count indirectly and build recursive models.
Explore 3 knowledge islands
Choose an island to read its lesson.
3 stages · 24 library problems · 108 checked variations · 2 × 6 assessment questions
Read the lessons →LEVEL 3 · DIFFICULTY 3/5 within this course
Structured Paths and Conditioning
Separate prefix constraints from conditional sample spaces.
Explore 3 knowledge islands
Choose an island to read its lesson.
3 stages · 24 library problems · 108 checked variations · 2 × 6 assessment questions
Read the lessons →LEVEL 4 · DIFFICULTY 4/5 within this course
Generating Functions and Graphs
Translate algebraic coefficients and network structure into counts.
Explore 3 knowledge islands
Choose an island to read its lesson.
3 stages · 24 library problems · 108 checked variations · 2 × 6 assessment questions
Read the lessons →Progress earned through practice
Earn two independent practice stars and one application star, then complete the library skill check for that stage. The check covers the stage’s library prompts, so changing numbers alone is not enough. Hints help you learn; your existing stars and earned rewards stay yours. Clear every stage to clear a level.
Every stage includes an explanation, two worked examples and eight library practice problems, plus checked variations with changing numbers and applications. Each level also has a separate unit test and a later review form. Parents see actual attempts, hint use and results.
These are independently authored core-skills courses, with the current scope listed for each course. They do not reproduce complete textbook contents. Difficulty describes the teaching sequence within each course; course preparation matters when comparing subjects. This site is not affiliated with or endorsed by AoPS. Results reflect these exercises and are not standardized scores. Content release math-courses-2026.09.27-university-guides-v2.