A wooden tray contains : 1) ten bars of each colored bead bars 1-9 in a wooden compartment box; 2) 5 bars of each of the grey bead bars 1-9 in a wooden box; 3) black and white bead stairs 1-9, plus 20 golden bead bards of 10 in a wooden compartment box. 1. Introduces the child to the unit combination of subtraction. 2. Teaches how to subtract concrete representation of negative functions. 3. Preparation for algebra (equal quantities of opposite sign eliminate each other).
