The first numbers that we are introduced to from an early age are 1, 2, 3, 4 etc.
These are called the 'Natural numbers', and can be placed on a number line from 1
to infinity. The natural numbers, in order, are always 1 whole number larger or
smaller than the next.
When we add or subtract the natural numbers the answer is always a natural
number. If we use subtraction or division however, we would without any other
system, not always be able to obtain an answer within the natural number system.
The sum 8 minus 10 for example would be impossible therefore a new number
system is needed. Suggate (1998, p.40) uses temperatures below freezing as an
example. In this instance we record how many degrees below O°c it is by counting
backwards from 0, to the left, using the 'negative' numbers. The integers are all
positive and negative whole numbers including 0 but the positive integers are also
natural numbers.
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