I am creating an app for multiplication learning/practice. During practice students get hints if they do not answer the question within some time or if they provide a wrong answer. These hints are tied into learning strategies presented separately via a number of learning activities; the goal is to remind the student of a strategy they learned about before.
I was wondering if anybody has recommendations for x8 multiplication strategies (I am looking for things anchored in research, not reciting/memorization tricks). Any pointers to papers, resources, etc. are highly appreciated.
As an example, a strategy for multiplying by x9 could be to get to the closest known answer, in this case by multiplying by 10 and then subtracting the other factor (e.g. 6*9 = 6 * (10 - 1) = 6*10 - 6 = 60 - 6 = 54.
EDIT 1: Focus is on single-digit multiplication. As for the comment about the research, perhaps let me restate that I am NOT interested in memorization tricks or anything that's not based in math (e.g. reciting, etc. I've seen a number of things that may make student memorize the fact, but they may not have a clue why that's the result). (Given the audience on stackexchange maybe that comment was not needed)