Definition

An efficient and uniform system for representing only ten digits (0, 1, 2, 3, 4, 5, 6, 7, 8, 9), any number can be represented as a string of digits.

Characteristics

• Each digit represents a value that is dependent upon its place in the string.
• The value represented by each place is always 10 times the value represented by the place to its immediate right.
• When moving one place to the left, the value is multiplied by 10. When moving one place to the left, the value is divided by 10.

Examples

Whole numbers

See Prezi presentation for decimal numbers

Non-Examples

• Roman numerals (XIV)
• binary (011001)
• tally marks

Definition

Whole numbers and their opposites

Characteristics

• Positive, negative, and zero

Examples

• Thermometer (-1 degrees)
• Stock market (down 2)
• Elevation (45 feet high)

Non-Examples

• 0.56
• √2
• ½

Definition

A rational number is a number that can be expressed as a fraction p/q where p and q are integers and q≠0.

Characteristics

• The word rational is derived from the word ratio
• Rational numbers include whole numbers and numbers with a repeating or terminating decimal
• Rational numbers can be plotted on a number line

Examples

• 25
• 1.25
• 11/2
• 5/6
• 0.23452345...
• -23
• √25

Non-Examples

• π
• √2
• e
• (1+√5)/2

Definition

An irrational number is a number that cannot be expressed as a fraction p/q where p and q are integers and q≠0.

Characteristics

• Irrational numbers can’t be expressed as repeating or terminating decimal

Examples

• π
• √2
• e
• (1+√5)/2

Non-Examples

• 25
• 1.25
• 11/2
• 5/6
• 0.23452345...
• -23
• √25