Topic 01
Numbers
The world is made of numbers. Slide along the number line, stack place value blocks, and slice up fractions until they make sense in your hands.
The Number Line
Drag the dot or tap a number
Distance from 0
0
Sign
Zero
Doubled
0
Place value blocks
Each column counts something different
Hundreds
1
1 × 100 = 100
Tens
4
4 × 10 = 40
Ones
7
7 × 1 = 7
100 + 40 + 7 = 147
Fractions
Top counts the slices, bottom is total slices
Slices filled
Total slices
That's 38% of the pizza
Suggested path
Counting & numerals
Where it all starts — the names of numbers, how digits build them, and the chart kids colour at school.
Counting
1, 2, 3 — tap to count, hear the rhythm, watch the blocks stack up.
Colorable number chart
1 to 100 in a 10×10 grid. Click cells to colour them and spot patterns.
Skip counting
2, 4, 6, 8 — pick a step and watch a marker hop along.
Numerals & digits
What's the difference between a number, a numeral, and a digit?
Compose & decompose
Break 47 into 4 tens + 7 ones — and put it back together.
Place value
Why 305 isn't the same as 350 — see digits move between columns.
The four operations
Add, subtract, multiply and divide — with blocks you can drag and tables you can sprint through.
Addition
Count two stacks of blocks together — see how + works as combining.
Subtraction
Take some away. Watch the blocks vanish and what's left appear.
Multiplication
3 × 4 is a rectangle of dots. Drag the sides and watch the total.
Long multiplication
Two-digit × two-digit, step by step on a grid.
Division
Share 12 cookies between 3 friends — see division as fair sharing.
Long division
Divide, multiply, subtract, bring down — the four-step dance, animated.
Times tables
1× to 12× in a clean grid. Hover any cell to see the row × column highlight.
Order of operations
PEMDAS — brackets first, then powers, then × and ÷, then + and −.
Number line & integers
Negatives, positives, and the line they all live on.
Fractions, decimals & percentages
The same idea — a part of a whole — said three different ways.
Fractions
Slice a circle, compare halves and thirds, add fractions visually.
Decimals
Tenths, hundredths, thousandths — and why they line up.
Percentages
Per-cent means per-hundred. Slide it and see it.
Ratios & proportion
Two cups flour to one cup sugar — scale the recipe and watch the ratio hold.
Estimation & ordering
Quick smart guesses and putting numbers in the right order.
Special numbers
Primes, π, e, φ — the celebrities of the number world.
Prime numbers
Find primes with the Sieve of Eratosthenes — interactive.
Factors & multiples
GCD, LCM and divisibility rules — the hidden structure of numbers.
Square & cube roots
What number times itself is 16? See roots as the inverse of powers.
Pi (π)
Roll a circle once — its diameter fits π times around. Watch it happen.
Euler's number (e)
The number that makes growth its own slope. 2.71828… and counting.
Golden ratio (φ)
1 : 1.618 — the rectangle that nests inside itself forever.
Fibonacci sequence
1, 1, 2, 3, 5, 8 — each one is the previous two added.
Cardinal, ordinal & nominal
Three (3), third (3rd), bus #3 — same digits, different jobs.
Factorial (n!)
5! = 5×4×3×2×1 = 120. Click and watch the tree fan out.
Irrational & real numbers
The numbers whose decimals never settle down — and the family that contains them all.
Number theory
Modulo arithmetic, divisibility rules, and the patterns hiding in whole numbers.
Other number systems
Computers count in 2s, designers in 16s, Romans in letters — flip a number between alphabets.
Binary
Computers count in 0s and 1s. Toggle 8 bits and read the decimal.
Hexadecimal
Base 16 — A through F take over after 9. Drives all those CSS colours.
Number bases
Base 2, base 5, base 10, base 16 — pick a base and convert any number.
Roman numerals
I, V, X, L, C, D, M — type a year and watch it become a Roman numeral.
Abacus
The original calculator. Click beads and read the number off.