Natural Numbers Keywords

Prime Number

A Prime Number can be divided evenly only by 1, or itself. And it must be a whole number greater than 1.

Prime Factor

A factor that is a prime number: one of the prime numbers that, when multiplied, give the original number. Example: The prime factors of 15 are 3 and 5 (3×5=15, and 3 and 5 are prime numbers).

Composite Number

A whole number that can be divided evenly by numbers other than 1 or itself. Example: 9 can be divided evenly by 3 (as well as 1 and 9), so 9 is a composite number. Whole numbers above 1 are either composite or prime.

Even Number

Any integer (not a fraction) that can be divided exactly by 2. The last digit is 0, 2, 4, 6 or 8

Odd Number

Any integer (not a fraction) that cannot be divided exactly by 2. The last digit is 1, 3, 5, 7 or 9

Ascending

Becoming bigger

Descending

Becoming smaller

Factor

Factors are numbers you can multiply together to get another number: A number can have MANY factors! Example: What are the factors of 12? 3 and 4 are factors of 12, because 3 × 4 = 12. Also 2 × 6 = 12 so 2 and 6 are also factors of 12. And 1 × 12 = 12 so 1 and 12 are factors of 12 as well.

Estimating

Finding a value that is close enough to the right answer, usually with some thought or calculation involved.

Place Value

In the number 555, each 5 in a different place has a different value. This is referred to as place value.

Indices

Indices is the plural of index

Consecutive Numbers

Numbers which differ by one are called consecutive numbers, e.g., 5, 6, and 7 are consecutive numbers.

Highest Common Factor (HCF)

The highest number that divides exactly into two or more numbers. When we find all the factors of two or more numbers, and some factors are the same ("common"), then the largest of those common factors is the Highest Common Factor. Abbreviated "HCF". Example: the HCF of 12 and 16 is 4, because 1, 2 and 4 are common factors of both 12 and 16, and 4 is the greatest.

Rounding

Rounding means making a number simpler but keeping its value close to what it was. It is the best known estimation method. Example: 73 rounded to the nearest ten is 70, because 73 is closer to 70 than to 80. But 76 goes up to 80.

Lowest Common Multiple (LCM)

The LCM of two or more numbers is the smallest number that these numbers will divide into exactly. Example: the Lowest Common Multiple of 3 and 5 is 15, because 15 is a multiple of 3 and also a multiple of 5. Other common multiples include 30 and 45, etc, but they are not the smallest (lowest).

Quotient

The answer after you divide one number by another

Product

The answer when two or more numbers are multiplied together.

Natural Numbers

The natural numbers are represented by the set N={1, 2, 3, 4, 5, 6, 7,...} This is an infinte set.

Square Number

The number we get after multiplying an integer (not a fraction) by itself. Example: 4 × 4 = 16, so 16 is a square number.

Power/index/Exponent

The power/index/exponent of a number says how many times to multiply the number by itself. It is written as a small number to the right and above the base number.

Sum

The result of adding two or more numbers.

Multiple

The result of multiplying a number by an integer (not by a fraction). Examples: • 12 is a multiple of 3, as 3 × 4 = 12 • −6 is a multiple of 3, as 3 × −2 = −6 • But 7 is NOT a multiple of 3

Difference

The result of subtracting one number from another. How much one number differs from another. Example: The difference between 8 and 3 is 5.

Order of Operations (BIRDMAS)

The rules that say which calculation or operation comes first in an expression: - Brackets - Indices - Roots - Multiplication & Division (work from the left) - Addition & Subtraction (Work from the Left)

Square Root

The square root of a number is a value that, when multiplied by itself, gives the number. Example: 4 × 4 = 16, so a square root of 16 is 4. Note that (−4) × (−4) = 16 too, so −4 is also a square root of 16. The symbol is √ which always means the positive square root.

Significant Figures

The word significant means: having meaning. With the number 368249, the 3 is the most significant digit, because it tells us that the number is 3 hundred thousand and something. It follows that the 6 is the next most significant, and so on.

Twin Primes

Twin primes are a pair of primes that differ by 2. For example, 3 and 5 are twin primes. So are 17 and 19.