Domain-level assessment
Number Theory Unit Test
22 questions, Medium difficulty and up — nothing easy here. Most questions deliberately combine two of the domain's 8 lessons in a single problem: a Diophantine equation that needs the Euclidean algorithm to actually solve, the Chinese Remainder Theorem combined with Fermat's little theorem to handle a composite modulus, a divisor-counting argument built on a GCD/LCM relation. Like the Algebra Foundations unit test, this checks whether the material holds up once nothing is telling you which lesson a problem came from.
Before you start
Questions appear in a fixed mixed order, and none of them name the technique they want — no "using the Euclidean algorithm" or "by CRT" in the problem text itself. Recognizing the right approach, and recognizing when a problem needs more than one, is itself part of what's being tested. Each question is tagged with every lesson it draws on (visible after you answer), so a pattern of misses points to exactly which lessons are worth revisiting.
Test
Same rules as every lesson quiz: up to three tries per question, then the full solution. Every answer here is a single number.