Addition
The important rule of addition (“plus-calculation”) is:
$\text{summand} + \text{summand}$ $= \text{sum}$At addition, the operands are designated as summand. The sum is the result.
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The sign
- If the summands have the same sign, you set the common sign and add the contributions.
- If the summands have different signs, you set the sign of the larger summand and subtract the smaller amount from the larger one.
Examples
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Set the common sign and add the contributions
$(-5)+(-3)=-(5+3)=-8$
$(+3)+(+6)=+(3+6)=+9$ -
Set the sign of the larger summand and subtract the smaller amount
$(-8)+(+3)=-(8-3)=-5$
$(+7)+(-9)=-(9-7)=-2$
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Mathematical laws
If $a$, $b$ and $c$ are rational numbers, you have to consider these following mathematical laws:
- Commutative law: $a+b=b+a$
- Associative law: $a+(b+c)=(a+b)+c$ $=a+b+c$