This article is a description and discussion of a design research project in which we introduced a research idea about the influence of language on number concepts development into praxis on a school in grades K-3. Danish children have difficulties remembering the Danish number names because the Danish language resembles a primitive number concept in mathematical thinking. Inthe project, we renamed the numbers between 11- 99 after the base-10 system. Our hypothesis was that this system would help Danish students to get a more secure concept about the base-10 system.The project lasted for three years ending in spring 2016. Our results were so convincing that the school decided to continue using the mathematical number names, and other schools that heard about the project seem to be interested in using the system as well. In other words, the project goes from being a top-down project to a bottom-up project.Keywords: , ,