5 smallest yellow cylinders.

Example of a practical exercise:

With the red, yellow and green boxes:

1. Go to the shelf with the child
2. Sit at a table, say the name of the activity: "These are the colored cylinders, and what color are these ones?"
3. Remove the lid and place it under the box
4. Take out all the cylinders one by one slowly, close the box and set it aside
5. Grasp the thickest cylinder and place it on our left
6. Each time choose the thickest cylinder among those remaining on the table and continue the gradation this way from thickest to thinnest, placing each cylinder next to the following one
7. Once it is done, look at the child and invite them to do it; for this, mix up the cylinders again
8. When the child has finished the gradation, ask them to fetch another box, the yellow or the green one (not the blue)
9. Open the lid of the yellow box, place it underneath and take out all the cylinders one by one, arranging them randomly on the table
10. Close the box and set it aside
11. Make the gradation with the red cylinders, then place the yellow gradation next to the red one
12. Invite the child to look at each side of the gradation, then suggest they do it in turn
13. Mix up all the cylinders again, and once the child has completed the two gradations by placing the cylinders on top of each other, take the two mirrors and place one at each end of the gradation. Ask them what they see (the cylinders to infinity)
14. Suggest the child go and fetch the green box
15. Place the yellow gradation next to the red one and invite the child to make the gradation with the green cylinders
16. Place the two mirrors on each side and look
17. Invite the child to do the same

With the blue box:

1. Take the cylinders out of the box and make the gradation, always from thickest to thinnest
2. Invite the child to do it.