Two wooden boards have the numbers 1 to 18 engraved above a grid of 10x18 squares. The engraving changes intensity across the board and the grid is divided vertically in two parts. Two sets of coloured strips are included. The first box contains nine blu and nine red strips with the numbers 1 to 9 engraved on one end of the strip.The other longer box contains 18 white strips from 2 to 36 cm long, used in subtractions. All wooden parts are UNI EN 71-3 finished.
ADDITION AND SUBTRACTION BOARDS WITH STRIPS
Working with these boards enables the child to memorize the results of additions and subtractions of small numbers by repeating the exercise. In addition the vertical line engraved between 10 and 11 shows the key passage through the 10. On the subtraction board this line is engraved between 9 and 10 and emphasizes the need to first take away the units beyond the 10 and then make the subtraction within the 10, thus breaking up the subtrahend in two numbers.