casting out 9's....

[kfeusse]

does anybody REALLY use this to check math problems?   just curoius.

[lots of little ducklings]

Lol. The family I used to tutor used abeka, but totally skipped this. I happily followed suit. Not sure any of us adults ever even figured out *how* to do it, and there were something like 8 graduate degrees between us all. :-)

[kiana]

Yeah, I use it, but you really don't need it.

 

If I were doing bookkeeping without a calculator you're darn straight I'd use it, but there's not a lot of need for that outside Amish communities and the like.

[Joker]

We used it here and there for fun. Youngest dd really liked doing it.

[klmama]

I thought Abeka was the only program that still used it. It's a fun trick, if you like that sort of thing. If not, skip it.

[....]

I think we encountered this in one of the Life of Fred books...Jellybeans or Kidneys, maybe??  I can't remember.  Anyway, I had never heard of it, either.  My son thought it was interesting. 

[AmericanMom]

My kids have had to use it in factoring. It's a quick way to see if 9 is a factor of a big number, along with the other tricks for other numbers, and I don't allow calculators until algebra 1, and then only for super messy numbers. There are lots of times a calculator is slower than mental math, in real world problem solving. Just my two cents, I know I am pretty old fashioned. But my father can solve most complicated math problems in his head faster than I can get out a calculator and plug in the numbers, and it keeps one's brain exercised as well. My dh is faster than my calculator too, though not quite as fast as my father. I didn't get quite that good an education in mental math, but I want that for my kids. He was in one of those tiny country schools a long time ago where they had to do compound interest problems in their heads and such. Amazing.