On Friday 14 August 2009 16:21:18 Pierre Abbat wrote: > Schools should teach metric > first, and delay old units until the children have shown that they can > multiply three-to-eight-digit numbers correctly by hand
I wrote that while trying to hurry up for an errand. A better explanation: Students should be taught metric as the primary measurement system, and customary only as conversions. All conversion factors must be exact (except the irrational ones, such as circular mils to square millimeters). Measuring tools should indicate only metric. If a math problem has a non-metric unit in the data, the answer must be in metric (or in units allowed with SI units), and the student should use the exact conversion factor and round at the end. The conversion factor for the pound has eight significant digits; so the pound can't be introduced until students can multiply eight-digit numbers. The conversion factor for the inch has only three significant digits, so it can be introduced earlier. In home economics, there should be no measuring spoons, and measuring cups should be used only for water. Everything else is weighed in grams. Once all new manufacturing and commerce is metricated, inches and pounds can be relegated to a college course for those, such as surveyors, who need to know them. Surveyors a hundred years hence are still going to run into maps measured in feet and chains. Pierre
