Blog Post
KatieGibbs-4b91
Community Member
Hi Hilla! This blew my mind! I would love to have had the option to review the method--I got the first question right and thought I understood but then was confuse on the others but couldn't go back to review. I just love these math "tricks." I never learned this one, but I did learn something similar to multiply by nines. I tried to teach it to a kid I was tutoring and then realized I had forgotten it!
PS. I think I accidentally clicked on REPORT when I went to click on REPLY! Must have been a Freudian slip of the mouse--trying to report myself for not learning well enough!
Great module and fabulous graphics to represent the trick!
PS. I think I accidentally clicked on REPORT when I went to click on REPLY! Must have been a Freudian slip of the mouse--trying to report myself for not learning well enough!
Great module and fabulous graphics to represent the trick!
HildegardSchleg
4 years agoCommunity Member
Hi Katie, thanks so much for your feedback. I agree that a review button could be useful. I'll add it. On the other hand, a little bit confusion can strengthen the learn experience, I guess :). I heard about this trick through a German book, so I can't copy it for you easily. Try this literature for more information: Digital Computer-Nonelectric (in Mathematics Teacher, April 1961) by Ferd W. McElwains and Mathematics in Fun and in Earnest by Nathan Court. There you also find a description of the method for higher numbers as 17X19 etc..
PS: If you don't mind that the explanation is written in German, let me know. I'll sent you a copy!