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• Addition and subtraction

• Multiplication and division

Rational numbers (the quantity is indicated by a ) are shown with algebraic signs and amount or just are just indicated by the amount (the amount is either a natural number or a fraction). Negative rational numbers are indicated by a “-“ in front of the amount and positive numbers can (not obligatory) be indicated by a “+” sign. The zero has no algebraic sign in front of it, since this number is neither positive nor negative.

To each rational number there is a opposite number. The opposite number to a rational number x is – 1 ∙ x (= – x). The opposite number has the same amount as the original number. Zero has no opposite number (or we could say that that the opposite number is also zero).

The number and the opposite number lie, in a geometrical aspect, symmetrical to zero. The amount of a number shows the distance between it and zero. The amount of a number x is shown as follows: | x | and is equal to x.

The natural numbers and their opposite numbers build the amount of  together (the whole number).

 = { …, – 3, – 2, –1, 0, + 1, + 2, + 3, …}

The number that lies the furthest to the left of the number line is smallest. This means that the positive numbers with a large amount are bigger and negative numbers with a small amount are bigger.

Copyright © 2005 Christian Franzki - Emkacom Group
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02/09/07