NUMBERS
Contents:
Definition:
Natural Numbers: basic counting numbers: ie.1, 2, 3....
- Integers: all positive and negative natural numbers: ie. ....-4, -3, -2,
-1, 0, 1, 2, 3....
- Real
Numbers: numbers that are integers and all numbers
in between, includes decimals: ie. ....2.1, 2.2, 2.3....
- Rational
Numbers: are real numbers as a ratio of two
integers: ie. 5/4 = 1
25.
- Irrational Numbers: are real numbers that cannot
be written as a ratio of two integers: ie.
5 = 23606......
the decimal never terminates nor repeats.
- Even
Numbers: integers that are divisible by 2: ie.
-4, -2, 0, 2, 4, 6....
- Odd Numbers:
integers that are not divisible by 2: ie. -3, -1, 1, 3,
5....
- Factor:
is a number that will divide exactly into another number
with no remainder: ie. 6 is a factor of 18 as it will go into 18 exactly 3
times.
- Multiple: is a number which is formed by multiplying two of more factors:
ie. 18 is formed by 6 times 3.
- Prime
Number: is a number which has 2 factors only,
the number itself and one: ie. 7 is a prime number with only two factors;
7 and 1.
- Square
Number: is a number formed by multiplying a
number with itself: ie. 16 is formed by 4 times.
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Approximation
Irrational numbers are approximated to a
required number of decimal places, note that a decimal figure
ending in 5 or above is rounded up, or if ending in a 4 or below,
is rounded down. ie. 2435 rounded
to 2 decimal numbers becomes 244, and 2432 rounded to 2 decimal numbers becomes 243.
Example: 235423333...
Three decimal places: 2
35423333
= 2 354
Two decimal places: 2
35423333 = 2
35
One decimal place: 2
35423333
= 2
4
Whole numbers only: 2
35423333
= 2
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Significant Figures
A number may be expressed as a given number
of significant figures, ie. 24545 has 5 significant figures, starting
from the most significant (far left) and counting towards the
right. If this is to be given as 3 significant figures it would
read 24500.
With small numbers the first figure counted
can not be a zero, therefore 00056
has only 2 significant figures (the 5 and the 6).
The small exercise shows how this operates
with a large number:
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