50 leçons gratuites, de la maternelle à la trigonométrie
Apprenez les maths à votre façon
Leçons de mathématiques gratuites et en langage simple pour enfants, ados et adultes — désormais du comptage jusqu'à la trigonométrie. Chaque leçon propose des exercices notés qui vérifient vos réponses et des schémas interactifs.
Parcourir par niveau
Petite enfance (M–CP)
- Additionner & soustraire
- Valeur positionnelle
- Du dénombrement à la multiplication
- Tables & division
- Fractions & décimaux
- Périmètre & aire
- Facteurs & nombres premiers
- Négatifs & priorités
- Variables & équations
- Ratios & pourcentages
- Angles, triangles & cercles
- Statistiques de base
- Graphes, systèmes & trinômes
- Polynômes & factorisation
- Pythagore & trigonométrie
- Probabilités & dénombrement
- Calcul mental dans les deux sens
- Estimation & problèmes
- Binaire, flottants & modulo
Arithmétique — dans les deux sens
Addition — carry right
The classic column method: ones first, carry to the left.
Addition — biggest first
Left-to-right addition: hundreds, then tens, then ones.
Subtraction — borrow right
The standard borrowing method, step by step.
Subtraction — left to right
Count down by chunks, or biggest column first.
Multiplication — standard way
Right-to-left multiplying with carrying.
Multiplication — biggest first
Partial products left to right — the mental-math way.
Division
Long division, short division, and chunking.
Algèbre
Variables & expressions
Letters that hold numbers — evaluate and translate.
One-step equations
Undo one thing: the balance rule that starts algebra.
Two-step equations
Undo in reverse order — with step-by-step checking.
Inequalities
<, >, ≤, ≥ — and the one rule that flips the sign.
Exponents & powers
Repeated multiplication, the three rules, x⁰ and x⁻ⁿ.
Square roots
Perfect squares, estimating, and simplifying √12.
Polynomials
Terms, degrees, like terms, and distributing.
Factoring
GCF, x²+bx+c, and difference of squares.
Graphing lines
y = mx + b — slope and intercept on the plane.
Systems of equations
Substitution, elimination, and where lines meet.
Quadratic equations
Parabolas, zero-product, and the formula that always works.
Géométrie
Angles & lines
Acute to straight, complements, parallel lines.
Triangles
The 180° rule, families, and why bridges trust them.
Quadrilaterals
The four-sided family tree and the 360° rule.
Circles
Radius, diameter, π — C = πd and A = πr².
Perimeter & area
Around vs inside — with unit-square grids.
Surface area & volume
Wrapping vs filling — boxes, cylinders, unit³.
The coordinate plane
(x, y) addresses, quadrants, distance.
Transformations
Slide, flip, spin, scale on the grid.
Pythagorean theorem
a² + b² = c², triples, and the distance formula.
Similarity & congruence
Same shape, different size — scale factors.
Nombres & structure
Place value & bases
Why 467 means 400 + 60 + 7 — and how binary works.
Fractions
What numerator & denominator mean, adding, comparing.
Decimals & percents
Place value past the point; everyday percent tricks.
Negative numbers
The number line, and why neg×neg = pos.
Order of operations
PEMDAS honestly — including the ambiguous case.
Factors & primes
Divisibility tricks and prime factorization.
Ratios, données & hasard
Ratios & proportions
Comparing quantities and cross-multiplying.
Unit rates & percents
Per hour, per dollar — and the better-deal test.
Statistics basics
Mean, median, mode, range — and when the mean lies.
Spread & deviation
Variance and standard deviation as 'typical distance.'
Probability basics
0 to 1 — favorable/total, complements, AND/OR rules.
Counting principles
Permutations, combinations, factorials.
Trigonométrie
sin, cos, tan
SOH-CAH-TOA on right triangles — sides and angles.
The unit circle
(cos, sin) as a point — and the free identity.
Capacités de raisonnement
Estimation & rounding
Front-end estimating and Fermi problems.
Word problems
Pólya's four-step method for attacking any problem.
Data, averages & graphs
Mean vs median — and how charts can politely lie.
Maths en sciences & informatique
Scientific notation & SI
Writing the universe's biggest and smallest numbers.
Measurement & error
Accuracy vs precision, significant figures, honest numbers.
Math inside computers
Binary, bits, floating point — and 0.1 + 0.2 ≠ 0.3.
Binary & hexadecimal
How computers count — $FF and 0x10 explained.
Floating point
Why 0.1 + 0.2 ≠ 0.3 — and the integer-cents trick.
Modular arithmetic
Clock math — MOD, parity tests, wrap-around indexing.
Deux directions, même réponse
La plupart des manuels ne montrent que la méthode de droite à gauche. Pourtant les calculateurs mentaux aguerris travaillent souvent dans l'autre sens : la plus grande valeur d'abord. Aucune n'est meilleure ; c'est la même arithmétique vue des deux bouts.
Pourquoi deux méthodes ?
La recherche montre que les stratégies de gauche à droite inventées par les enfants sont courantes et améliorent la compréhension de la valeur positionnelle. →
📚 Recherche & lectures — articles et livres réels, avec liens.