Math & Numbers Facts for Kids
Mind-bending number facts
Most internet security is based on the mathematical difficulty of factorising very large numbers into primes. Even the world's fastest computers would take longer than the age of the universe to crack modern encryption.
Long division has been used since at least the 12th century, when it was introduced to Europe via Arabic texts. The modern written method was standardised by mathematicians during the Renaissance.
The Sieve of Eratosthenes is a method for finding all prime numbers up to any limit by crossing out multiples of each prime. The Greek mathematician Eratosthenes invented it around 240 BC.
A leap year occurs every four years to account for the fact that Earth takes 365.25 days to orbit the Sun. However, century years are only leap years if divisible by 400 β so 2000 was a leap year but 1900 was not.
Angles have different names depending on their size: acute (less than 90Β°), right (exactly 90Β°), obtuse (between 90Β° and 180Β°), and reflex (more than 180Β°). A straight line is 180Β° and a full turn is 360Β°.
The difference between consecutive square numbers (1, 4, 9, 16, 25β¦) is always an odd number: 4β1=3, 9β4=5, 16β9=7. The differences form the sequence 3, 5, 7, 9 and so on.
The place-value number system we use today, where the position of a digit determines its value, was developed in ancient India. It was later transmitted to Europe by Arabic scholars.
The volume of a sphere is calculated using the formula V = (4/3)ΟrΒ³. Archimedes was the first to prove this, and he considered it one of his greatest discoveries.
The Collatz conjecture says: take any positive whole number, if it is even halve it, if it is odd multiply by 3 and add 1, and repeat β you will always eventually reach 1. This has been tested for trillions of numbers but no one has proved it is always true.
In Euclidean geometry, parallel lines never meet, no matter how far they are extended. However, on a curved surface like the Earth, lines of longitude are parallel at the equator but all meet at the poles.