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A number represents a quantity, it is written with digits. It can be broken down into a sum of two numbers.

This animation proposes three representations of the concept of addition:

- A collection of pellets represents a whole to be divided into two parts.
- Three numbers are symbolically linked when the whole (blue number) represents the sum of the two parts (yellow and red numbers).
- A mathematical representation associates numbers (operands) and signs (+, =).

Links are broken if :

- The whole counts too many elements (blue pellets remain visible).
- The whole does not count enough elements (clear pellets are visible).

When the links are established, it is possible to display all the decompositions of the same number by clicking on the pellets of the collection.

A part is also interpreted as the result of a subtraction.

- To break down a number into two parts.
- To interpret the addition as the pooling of two sets of elements.
- To develop calculation strategies.
- To define the addition and subtraction operations.