On a question
At the beginning of game children most often make that mistake that instead of the biggest put in the basis the secondlarge cube, and on it put the first do not distinguish two biggest cubes.
I noticed that the same mistake was made also by backward children at experiences which I did with de Sanctis's device.
On a question What biggest?
the child took not the biggest, and following in size.
Any of four sets can be used and for other game.
Whetstones can be mixed on a rug or on a table and to put them as it should be on other table at some distance.
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