Teaching the Controversy: Is 5 × 3 Five 3s or Three 5s?
"It is a basic fact of math that it doesn’t matter what order you multiply numbers in. Multiplication commutes: three groups of five has the same number of objects as five groups of three. It’s easy to feel outraged that the student was punished when their answer was correct. Hemant Mehta wrote a lengthy post laying out some reasons the teacher may have had for marking 5+5+5 incorrect. Mehta’s basic argument is that teachers are not only teaching students how to do problems now but preparing them for future math classes."
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This article from Scientific American dissects one of many homework assignments that have outraged parents recently, often with blame falling on the Common Core State Standards (CCSS). It firstly and correctly points out that the Common Core is not a curriculum and so there are flaws in many debates that stem from a misunderstanding of CCSS itself. Then the article examines several logical and pedagogical rationales at play.