Dividing by Nine: Something Cute (VIDEO!)

Here is something not too serious, but cute. To divide a number by 9, just add up its digits in turn! For example:

124 / 9 = “1 and 1+2 and 1+2+4″ = 13R7

Let’s explore why this little curiousity works.

Dividing by Nine

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  Written for educators - and their students too! - this website, slowly growing, takes all the content Tanton has developed in his books, videos, and workshops, and organizes it into short, self-contained, and complete, curriculum units proving that mathematics, at all points of the school curriculum, can be joyous, fresh, innovative, rich, deep-thinking, and devoid of any rote doing! Let's teach generations of students to be self-reliant thinkers, willing to flail and to use their common sense to "nut their way" through challenges, to assess and judge results, and to adjust actions to find success. (Great life skills!)

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• Books

  • Thinking Mathematics! (TEN VOLUMES)
  • Solve This: Mathematical Activities for Students and Clubs
  • Encyclopedia of Mathematics
  • Geometry I & II

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  Email: tanton.math@gmail.com