Editing Elementary arithmetic (section)

== Addition ==
[[File:Addition with carry.png|thumb|alt=Diagram of addition with carry|Example of [[Carry (arithmetic)|addition with carry]]. The black numbers are the addends, the green number is the carry, and the blue number is the sum. In the rightmost digit, the addition of 9 and 7 is 16, carrying 1 into the next pair of the digit to the left, making its addition 1 + 5 + 2 = 8. Therefore, 59 + 27 = 86.]]
{{Main|Addition}}
[[Addition]] is a mathematical operation that combines two or more numbers (called addends or summands) to produce a combined number (called the sum). The addition of two numbers is expressed with the plus sign (<math>+</math>).{{r|mpb}} It is performed according to these rules:
* The order in which the addends are added does not affect the sum. This is known as the [[commutative property]] of addition. (a + b) and (b + a) produce the same output.{{r|rosen|hall}}
* The sum of two numbers is unique; there is only one correct answer for a sums.{{r|hall}}

When the sum of a pair of digits results in a two-digit number, the "tens" digit is referred to as the "carry digit".{{r|rf}} In elementary arithmetic, students typically learn to add [[Integer|whole numbers]] and may also learn about topics such as [[Negative number|negative numbers]] and [[Fraction|fractions]].