Expert guides for parents, students and math enthusiasts. Algebra to Olympiads — we've got you covered.
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The goal was never to make kids faster at math — it was to make them fall in love with it. Speed is a byproduct of genuine understanding.

Dive into the subject you love most
Variables, equations, and the language of math
The square root of 361 is exactly 19 (19.0000), because 19 × 19 = 361. Below: four ways to find it, a ten-second check, and where 361 shows up.
The square root of 144 is 12 (12.0000 as a decimal), since 12 × 12 = 144. Inside: four ways to find it, why 144 is called a gross, and worked examples.
The square root of 324 is 18 (18.0000 as a decimal), because 18 × 18 = 324. Below: three ways to find it, the negative root, and worked examples.
Shapes, proofs, and spatial thinking
Geometry is the branch of mathematics that studies points, lines, angles, shapes, and space — how figures are built, measured, and related. This hub maps every geometry topic into ten clusters: foundations (points, lines, planes), angles, parallel lines and transversals, triangles, quadrilaterals and polygons, circles, 3D solids, coordinate geometry, conic sections, and transformations — each linking to a full guide with formulas and worked examples.

Collinear vectors are vectors that lie along the same line — which means one is always a scalar multiple of the other, a = k,b. This article covers the three tests for collinearity (scalar multiple, equal coordinate ratios, zero cross product), how collinear differs from parallel and coplanar, and worked examples.

Rotational symmetry means a shape maps exactly onto itself when turned about its centre by some angle smaller than a full turn. The order counts how many times it matches in one 360° rotation, and the angle of rotation is 360°/(order); this guide gives the definitions, six worked examples, and the traps that produce a wrong order.
Angles, waves, and circular harmony
Sec 3pi equals exactly -1 (decimal -1.0000). The angle 3π (540^°) ends on the negative x-axis, where cosine is -1; below are the proof, graph, examples and calculator traps.
Sin 2pi/5 equals (√(10 + 2√5))/4 ≈ 0.9511, the same value as sin 72^°. Below: the golden-ratio proof, the unit circle, why calculators sometimes show 0, examples and mistakes.
Sin 5pi = 0 exactly (decimal 0.0000). The angle 5π is coterminal with π, so this guide shows the unit-circle reason, the degree form 900^°, the graph, six examples and three common mistakes.
Raising confident, curious young mathematicians
Every essential formula, explained and derived
The semicircle formulas are: area = 1/2π r², arc length = π r, perimeter = π r + 2r = r(π + 2), and diameter = 2r. This article gives every semicircle formula, why each comes from the full-circle analogue, three worked examples spanning Quick to Stretch, and the single most common mistake students make — forgetting the diameter when computing perimeter.

The mean is the average of all values (Σx / n), the median is the middle value when data is ordered, and the mode is the value that appears most often. Use the mean for symmetric data, the median for skewed data with outliers, and the mode for categorical data. For moderately skewed distributions, the three are linked by Karl Pearson's empirical relation: Mode = 3 Median − 2 Mean.
The percentile formula tells you where a value stands in a dataset: P = (number of values below x)/N × 100. This article covers both directions — finding the percentile of a value, and finding the value at a given percentile — with worked examples, the percentile-versus-percentage distinction, and the mistakes that trip students up.
Crystal-clear definitions with worked examples

An irrational number is a real number that cannot be written as a ratio of two integers (p/q form), and its decimal expansion never terminates and never repeats. Common examples include √2, π, e, and the golden ratio φ.

An integer is a whole number - positive, negative, or zero - with no fractional or decimal part, written as the set ℤ = {..., −3, −2, −1, 0, 1, 2, 3, ...}. Integers follow closure, commutative, associative, distributive, identity, and additive inverse properties, and form the foundation for arithmetic, the number line, and all rational numbers.
The radius of a circle is the distance from its centre to any point on the boundary, and it is exactly half the diameter. This article covers the definition, the three formulas for finding the radius, how it ties to the circle equation, six worked examples, and the common mistakes.
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