Learning together - I had a student a few years back who told me the best gift he ever received was accepting Jesus in his heart. All I can say is.... he gets it! He taught me more that year that I could have ever taught him.
AFTER teaching students multiplication, this would be a good trick to teach them in order for them to check their answers. I would not want this to be the way that I taught them, but it could serve as more of an aid.