Math & Numbers Facts for Kids
Mind-bending number facts
An even number is any whole number that can be divided exactly by two with no remainder. The last digit of every even number is 0, 2, 4, 6, or 8.
Multiplication has two important properties: the commutative property (3 Γ 5 = 5 Γ 3) and the associative property ((2 Γ 3) Γ 4 = 2 Γ (3 Γ 4)). These rules make it easier to rearrange calculations mentally.
A ratio compares two quantities, such as 3:2, meaning for every 3 of one thing there are 2 of another. Ratios can also be written as fractions (3/2) and are used everywhere from cooking recipes to map scales.
The x-coordinate of a point is called the abscissa and the y-coordinate is called the ordinate. Together they are written as an ordered pair, such as (3, 5), always with x first.
A perfect square number can never end in the digits 2, 3, 7, or 8. You can use this trick to quickly check whether a large number could possibly be a perfect square.
A cube number is made by multiplying a number by itself twice: 1Β³=1, 2Β³=8, 3Β³=27, 4Β³=64, 5Β³=125. They are called cube numbers because they represent the volume of a cube with sides of that length.
The mathematician Brahmagupta of India was the first to write formal rules for arithmetic with zero in 628 AD, including that zero added to any number gives that number. This was a revolutionary idea at the time.
When rounding a number, if the digit being rounded is 5 or more you round up; if it is 4 or less you round down. For example, 67 rounded to the nearest 10 is 70, but 63 rounds down to 60.
Simultaneous equations involve finding values for two or more unknowns that satisfy all given equations at once. They are used in everything from navigation to economics.
The hypotenuse is always the longest side of a right-angled triangle and is always opposite the right angle. Its length can be found using Pythagoras' theorem: c = β(aΒ² + bΒ²).