Decimal notation and decade grouping are the basis of traditional elaboration of arithmetic. In the approach that we follow, this elaboration goes gradually through the didactical structuring and extending of number blocks. In this process of block extending, we use sums, applying the principle of permanence of the meaning of addition. Then, finding decimal notations for such sums is a purely calculation task, that is reducible to easier and smaller (already performed) cases. In this paper, the block 1-–100 is constructed as the extension of the block 1-–20 and its didactical analysis is executed. Due to pedagogical demands, we suggest the replacement of some arithmetic rules by their ``narrative'' substitutes that also have to be meaning-based.