The Number System

Things to remember

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• The Binary number system always uses only two different symbols ( the digit 0 and 1).
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• The Natural ( or counting) numbers are 1, 2, 3, 4, 5,  etc. There are are infinitely many natural numbers. The set of natural numbers, { 1, 2, 3, 4, 5, .........} is something written 'N' for short.
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• The integers are the set of real numbers consisting of the natural numbers, their additive inverse and zero.{......-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, }.
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• The rational numbers are those numbers which can be expressed as the ratio of two integers. For example, the fraction 1/3 and -1111/8 are both rational numbers.
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• An irrational number is a number that cannot be written as the ratio ( or fraction). In decimal form, it never ends or repeats. 
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