The orgin ofthis approach begins, like many of the others Facets The University of Chicago School Mathematics Project, That look place at the time of new math, in the late 1950s . Comprehension was interpreted at time primarily as knowing why mathematical properties worked or were true. Many people though at that time that if you “understood” –that is, if you knew the theoretical properties underlying the mathematics you were studying –then you would automatically gain the skills. It seemed reasonable –but it was –if you were higher up the taxonomy, you should be able to do the things that are lower –but it was not true. Students who were taught the properties but not taught the procedures simply did not develop paper and pencil skill. Even if they were taught the procedures, if they did not practice them, then they did not achieve a high level of competence