One half and one third
Use shapes and groups of objects to explore equal parts, then explain how to check the result.
Read the Vietnamese lessonClear reasoning · Independent thinking
Understand each step.
Build confidence in mathematics.
Free lessons, worked examples and practice. Choose your level; primary and lower-secondary resources are currently in Vietnamese.
Choose a learning level
Start with a grade or topic that matches what you want to learn. Each link shows the language of its resources.
Grades 1–5 · In Vietnamese
Primary mathematics
Explore number, shapes and measurement through guided examples, activities and practice.
Browse primary resources Grades 6–9 · In VietnameseLower-secondary mathematics
Build understanding of number and algebra, geometry, statistics and probability through examples and practice.
Browse lower-secondary resources High school · In EnglishHigh-school mathematics
Choose a topic, check the prerequisites and work through explanations, examples and practice.
Explore English lessonsExplore a lesson at your level
The primary and lower-secondary examples below are in Vietnamese. The high-school example is available in English.
Rounding decimals to a specified place
Start with a length and a number line, choose the nearer value, and practise checking rounded results.
Read the Vietnamese lessonOrthogonal projection of a point onto a plane in 3D
Use the plane’s normal direction to find the projection and check that it lies on the plane.
Read the English lessonWays to begin
Choose a starting point
Use these links to choose existing resources by grade or topic, revisit a skill, and learn at your own pace.
Grades 1–5 · In Vietnamese
Choose a grade or a foundational activity
Choose a grade, or start with an early mathematics activity. Use the parent guide when learning together.
Browse primary resources Grades 6–9 · In VietnameseReview a skill you need
Choose a grade, check the prerequisites and try the practice before opening the solutions.
Browse lower-secondary resources High school · In EnglishConnect topics through a learning path
Follow an existing English high-school path through prerequisites, worked examples and practice.
View English high-school pathsEnglish high-school lessons and learning paths
English high-school subjects
Browse topics with lessons already available in English.
164 English lessons available
5 lessons
Algebra & Equations
Quadratic equations, discriminants, signs of quadratic expressions, and equations involving radicals.
Explore this subject 30 lessonsAlgebra & Trigonometry
Algebraic equations, inequalities, powers, logarithms, and trigonometry.
Explore this subject 38 lessonsCalculus
Sequences and limits, derivatives, functions and graphs, antiderivatives, and integrals.
Explore this subject 5 lessonsComplex Numbers
Complex arithmetic, modulus, arguments, polar form, roots, and quadratic equations.
Explore this subject 9 lessonsCounting & Probability
Counting rules, permutations, combinations, binomial coefficients, events, and probability.
Explore this subject 36 lessonsGeometry & Vectors
Coordinate geometry, transformations, solid geometry, and vectors in two and three dimensions.
Explore this subject 4 lessonsPlane Transformations
Translations, reflections in a line or a point, and rotations in the plane.
Explore this subject 37 lessonsSolid Geometry & Vectors
Points, lines and planes in space; intersections, cross sections, parallelism, perpendicularity, angles, and distances.
Explore this subject 4 lessonsAdvanced Topics
Further reading on symmetry and finite groups, including cyclic groups and the quaternion group.
Explore this subjectEarly mathematics and Grades 1–9 resources are available in Vietnamese. This English library covers high-school topics.
Available in EnglishFree lesson
Random experiments, sample spaces, and events
Distinguish outcomes from events and use unions, intersections, mutual exclusivity and complements in finite sample spaces.
Read the lessonHigh-school learning paths · In English
Follow a high-school learning path
Three paths connect existing English high-school lessons through prerequisites, worked examples and practice.
9 lessons
From 3D coordinates to orthogonal projection
Use coordinates, dot products and the normal direction to project a point onto a plane and check the result.
View this learning path9 lessons
From counting to probability
Distinguish ordered and unordered counting models, then move from sample spaces to addition, conditional probability and multiplication.
View this learning path10 lessons
From limits and derivatives to graph sketching
Combine domains, limits, derivative signs and local extrema to read and sketch the function families studied.
View this learning pathRecently published English high-school lessons
Read a lesson and try its practice before checking the answers.
Random experiments, sample spaces, and events
Distinguish outcomes from events and use unions, intersections, mutual exclusivity and complements in finite sample spaces.
Read lessonThe addition and multiplication principles
Count disjoint alternatives and multistage processes, including numbers with leading-digit, parity and distinctness restrictions.
Read lessonConditional probability and independence
Define conditional probability with a positive conditioning probability and distinguish independent draws from transfer-between-box experiments.
Read lessonThe multiplication rule of probability
Use conditional probability chains and independence correctly, and combine products with disjoint cases.
Read lessonThree-dimensional Cartesian coordinates: points and vectors
Understand signed point and vector coordinates, orthonormal bases, and projections onto coordinate axes and planes.
Read lessonCross products and scalar triple products: formulas and applications
Calculate cross products and signed triple products to test dependence, collinearity and coplanarity, and find areas and volumes.
Read lessonFree practice · In Vietnamese
Understand the lesson. Try it for yourself.
Clear explanations, worked examples and short practice sets help learners study at their own pace. Try an approach, explain each step and check the result before opening the guidance.
The learning-materials team includes educators from Ho Chi Minh City University of Education, with doctoral and master’s degree holders and bachelor’s graduates with an Excellent graduation classification. The team also works together on in-depth mathematical research.
Start with one skill
Choose a short set in Tự luyện, currently in Vietnamese. Use hints when needed, compare your reasoning with the solutions and revisit the relevant lesson.
Explore Tự luyệnHow we develop lessons
Careful reasoning.
Independent thinking.
- Explain the mathematical relationships behind a formula.
- Work through examples and check the conditions used.
- Provide practice and solutions for comparison.
Common questions
Do I need to register to read the free lessons?
No. You can read the lessons, practise and download the published learning materials free of charge, without signing in.
Which educational levels does the library cover?
The free learning library includes early mathematics before Grade 1, resources for Grades 1–9 and high-school mathematics topics. Explore the full library (in Vietnamese) or the English high-school lessons.
Which resources are available in English?
Early mathematics and Grades 1–9 resources are currently in Vietnamese. High-school lessons are available in Vietnamese and English; not every lesson has both versions.
Where should I start?
Choose a topic and check the lesson introduction and prerequisites. You can follow a suggested learning path or revisit a skill you want to strengthen. For early mathematics and Grades 1–9, use the Vietnamese learning resources.
How can I report an error or suggest an improvement?
Email contact@cunghoctoan.com with the lesson title or web address and a description of the part that needs attention.
Have feedback about the materials? Send a suggestion or report an error.
Support when you need it
Learn with a teacher when you need help
Start with the free lessons and suitable exercises, especially Tự luyện. If you still have difficulty understanding a concept or explaining your solution, you can request an online class. We open classes only when learners genuinely need a teacher’s help to improve their learning.