Reply To: Algorithms Grades 2-5

#939
Bill McCallum
Keymaster

Whether and when to teach the standard algorithm was a hotly contested topic during the writing of the standards, and now some of that debate has transferred to the meaning of the term. Some think it is the algorithm exactly as notated by our forebears, some think it includes the expanded algorithm, where you write down all the partial products of the base ten components and then add them up. Ultimately this is a question that has to be settled by discussion, not fiat. My opinion is that the standard algorithm has two key features; like the expanded algorithm it relies on the distributive law applied to the decomposition of the number into base ten components, but in addition it relies on the fact that the order of computing the partial products allows you to keep track of the addition of the partial products while you are computing them, by storing the higher value digit of each product until the next product is calculated. I don’t think different ways of notating this constitute different algorithms. So, in particular, the algorithm that Scott was talking about, bottom of page 13 in the margin, would qualify in my opinion, but the partial product algorithm in the middle of that page would not.