The complete collection: 55 chapters, from grade 1 to grade 8 plus a grand finale, each told as a story by Erklärus and Liri. Choose your chapter – sorted by grade level.
Erklärus
9 years old · glasses · always has his notebook · can't sleep for all his questions
Liri ⭐
A star who lost his way · warm and golden · searching for his way home
🍎 For Parents & Teachers
The chapters follow the classic structure of European elementary and secondary school curricula (grades 1–8) and cover the mathematical foundations taught at this age across most European countries. They can be used both at home and in the classroom.
Every section has a read-aloud button 🔊 and interactive exercises to take part in, not just watch.
🗺️ The Chapters – a journey through mathematics
🏫 Elementary School (Grades 1–4)
Grade 1 — The very first steps
1
The Natural NumbersWhere it all begins
2
Comparison SignsGreater, smaller, equal
3
Addition Part 1Adding up to 20
4
Subtraction Part 1Taking away up to 20
5
First Geometric Shapes & PatternsCircle, triangle & co.
6
Working with MoneyEuros & cents
Grade 2 — The hundreds range & the times tables
7
The Natural Numbers up to 100Tens and ones
8
Addition & Subtraction Part 2Strategies up to 100
9
Multiplication Part 1From plus to times
10
Division Part 1Sharing fairly
11
Time and Time SpansHow long does the way take?
12
Symmetry & SolidsMirror images & 3D shapes
Grade 3 — The thousands range & written calculation
13
The Natural Numbers up to 1,000The place value chart
14
Written AdditionNumber range up to 1,000
15
Rounding Numbers & EstimatingWhen “about” is enough
16
Written SubtractionThe complement method
17
Lengths and WeightsFrom mm to km
18
Drawing with a Set SquareRight angles & parallels
Grade 4 — The millions range & great calculators
19
The Natural Numbers up to 1,000,000Up to a million
20
The Rules of ArithmeticMultiplication before addition
21
Written MultiplicationTwo lines, one result
22
Written DivisionThe master discipline
23
Square and RectanglePerimeter and area
🏫 Secondary School (Grades 5–8)
Grade 5 — Big numbers, tables & intro to geometry
24
ScaleA memory of a tiny map
25
Giant NumbersA remembered number becomes readable
26
Divisibility, Factors, Multiples & PrimesA remembered signal gets decoded
27
Multiplying and Dividing by 10, 100, 1,000…The trick with the zeros
28
The Coordinate SystemEvery point has an address
29
Cube and CuboidVolume and surface area
30
Data, Tables and ChartsA remembered pattern becomes visible
Grade 6 — The world of fractions & decimals
31
FractionsNumerator, denominator, simplifying
32
Calculating with FractionsPlus, minus, times, divided
33
Decimal Numbers & Place ValuesNumbers between the whole numbers
34
Calculating with DecimalsDecimal point under decimal point
35
Types of Angles, Measuring and DrawingAcute, right, obtuse
36
The TriangleAngle sum 180°
37
The TrapezoidTwo parallel sides
38
The ParallelogramA rectangle pushed sideways
Grade 7 — Logical thinking, percentages & negative numbers
39
Positive & Negative NumbersBelow zero, too
40
Rule of ThreeDirect proportion
41
Percentages & InterestHundredths & interest
42
Calculating with VariablesLetters as numbers
43
Solving EquationsThe balance in equilibrium
44
Geometric ConstructionsUsing compass and set square precisely
Grade 8 — Functions, roots & solid geometry
45
PowersBase to the exponent
46
Binomial FormulasThree formulas, one picture
47
Linear Functionsy = mx + b
48
Real Numbers & Square RootsWhen numbers never end
49
Linear Systems of EquationsTwo lines, one shared point
50
The CircleA remembered round window
51
PrismsA remembered crystal
52
The CylinderA remembered fuel tank
53
The PyramidA remembered lander module
54
The Pythagorean TheoremA remembered right-angled brace
🌟 The grand finale
🌟 Why mathematics as a story?
Numbers and formulas stay abstract unless someone explains what they're for. Erklärus and Liri give mathematics a face: every chapter is a little story in which a mathematical concept is needed to solve a real problem.
That way, “I have to learn this for school” becomes “I want to know how the story continues” – and the math comes along for the ride.
✨ More to discover
New chapters are added regularly. Check back now and then, or bookmark this page – so you'll always find Erklärus & Liri again.
