script src="https://polyfill.io/v3/polyfill.min.js?features=es6"> Definitions : Key Skills (or Basic Skills) in Application of Number (Maths)

## Definitions

### Numbers

 Even Numbers numbers divisible by 2 2,4,6,... Odd Numbers numbers not divisible by 2 1,3,5,7,... Whole Numbers 0,1,2,3,4,.....

• Integers include the whole numbers, but extend the range to include negative numbers.

• Prime Numbers are numbers with no factors other than 1 and the number itself.

• Rational Numbers are numbers that can be represented as a fraction. Integers come under this classification because, for example

$12 = \frac{12}{1}$

• The Reciprocal of a number is given by

$\mbox{reciprocal} = \frac{1}{\mbox{number}}$

For example :

The reciprocal of 3 is $$\frac{1}{3}$$

The reciprocal of 0.362 = $$\frac{1}{0.362}$$

### Operations

• The Sum of two numbers is the result of adding them

• The Difference of two numbers is the result of subtracting the smaller number from the larger number

• The Product of two numbers is the result of multiplying them

• The Binary Operators are   +,  -,  x ,  and $$\div$$

• An operation is Commutative if the order does not matter. Addition and multiplication are commutative, subtraction and division are not.

• A Factor of a number is a number that divides that number exactly.

### Fractions

• The top part of a fraction is called the Numerator
• The bottom part of a fraction is called the Denominator

### Prime Numbers

A prime number is a number that can only be divided by 1 and itself.

For example : 3, 5, 7, 11, 13, 17, 19

• 1 itself is not included as it does not have two factors.

Note

• The only even prime number is 2
• A product of prime numbers is, by definition, not itself a prime number

### Shapes

Shapes with all sides equal are called regular. Otherwise they are called irregular.

Shapes with 3 sides are called triangles. Regular triangles are called equilateral.

Shapes with 4 sides are called rectangles. A regular rectangle is called a square.

Four-sided figures with two pairs of parallel sides are called parallelograms