Age:
9-10 years

Aims:
To develop mental calculation

Materials:
Peices of coloured cards

Vocabulary:
Operator, mental calculation

Introduction:
The teacher hangs 10 numbers on the wall, asks students to discover the relationship that exists among them, and delivers arrows with operators.

Main part:
Students, using only mental calculation, trying each time to place between a number and another, the arrow with the operator that establishes the relationship among the 10 numbers arranged on the wall.

Round up:
Each time the operator is identified, the students explain how they achieved the result

Observations:
This exercise has proved useful for the consolidation of mental calculation and for the collaborative spirit emerged among students.