Vikas ( 11 years ago )
There is a lot of silly stuff they teach in algebra class, and that I had to teach in my tonirutg center, that comes from New Math of the '60s and the Bourbaki group's approach to math teaching. Both are highly formalized and deductive.If you ever had to learn what the commutative law was, it's their fault. You don't need that until you study linear algebra or abstract algebra, which few are going to do anyway.About closure, here's how I helped my students get it: to do a basic arithmetic operation, you need two numbers. You can't say, "What's 5 plus?" So, imagine you're taking these two numbers from a bag -- does the answer also come from that bag? If so, then the operation is closed for that bag. (That helps tie it in with the term "closure." You never leave that bag.) If you have to go to a different bag to get the answer, it's not closed.If you have a kid in algebra, or are a teacher, I've found that picture helps a lot.