I've been reading kindergarten and elementary math curricula, and one theme that comes up (besides trying to teach inches and centimeters at the same time) is nonstandard units. Why do they do this? When I was little, I used my hand in an L to estimate a decimeter. It is now 140 mm. My step is 678 mm, which is hard to compute with in my head (surveyors have to pace sometimes, and measuring the pace was an exercise in Surveying 1). Why don't they stick with standard units that don't change size as the child grows?
Pierre
