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Addition is the mathematical process of putting things together, that is to say joining. With the addition of two numbers, the process may be thought of moving a certain distance in the positive direction. If one considers the following equation:

$a + b = c$

The plus sign or addition symbol ( + ) marks that addition is preformed on its adjacent numerals (a and b). C is called the sum of a and b. This equation may be calculated by moving a, b whole units in the positive direction.

## Computation

Taking in account the analogy from the previous section,

$3 + 4 = ?$

may be thought of as moving 3 in the positive direction by 4 units:

$3 + (1+1+1+1)$

with may be counted to achieve the answer of 7.

## Properties

• Addition is commutative: $a + b = b + a$
• Addition is associative: $a + (b + c) = (a + b) + c$
• Addition has an identity element: zero.

## Estimation

Addition sums are possible to be estimated. It is done by rounding off each addend to the nearest n significant figures (where n is a whole number), and adding both of the rounded numbers.