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(17,542 posts)Our teachers would have considered that "cheating."
calimary
(81,298 posts)I forget which of them pointed it out, in which class, but yeah. Catholic school.
Marthe48
(16,963 posts)any number divisible by 9, no matter how many places, the digits add up to 9 (1,341, ,270, 81,000 for example) If you add the digits of 99, you get 18, which equals 9.
AZSkiffyGeek
(11,026 posts)0+9
1+8
2+7
calimary
(81,298 posts)I loved how that all worked, from top to bottom. Always nine.
Staph
(6,251 posts)With any number divisible by 3, if you add the digits, and then add the digits of the answer, ad infinitum, the answer will always be 3 (or a single digit number divisible by 3, like 6 and 9).
2022 -- 2 + 0 + 2 + 2 = 6!
Marthe48
(16,963 posts)Partly, because it is the sq. root of 9. I used to know a lot more about fun with numbers. My great aunt had several fortune-telling games based on numerolgy, maybe that's what got me interested
asiliveandbreathe
(8,203 posts)Just WOW!! and the down tweets ..
LetMyPeopleVote
(145,291 posts)Some of this I learned in class and some while competing in a contest called number sense where you did math problems in your head (no scratch pads).
TexasTowelie
(112,217 posts)particularly when conducting audits and reconciliations as I did throughout my career.
LetMyPeopleVote
(145,291 posts)niyad
(113,323 posts)If the difference in the two amounts is divisible by 9, there is a transposition error, and the number of digits in the answer tells you which columns.
liberalla
(9,249 posts)(didn't go any further)
Bev54
(10,052 posts)unc70
(6,115 posts)teach1st
(5,935 posts)The real trick, though, is letting the kids work in small groups to figure out why the pattern occurs and why only with nine. The small groups thing might not work in third grade, but it has worked - and been unsuccessful at times - in fourth and fifth grades.
BigmanPigman
(51,607 posts)my above average 6th graders got it.
wnylib
(21,479 posts)Instead, I was taught by rote. Fortunately, I have a good memory, but the rote method did nothing to develop any real understanding of numbers
In grade school, the teacher put addition "problems" across the top of the blackboard. For about a month in second grade, it would be 1+ the rest of the numbers up to 9, and 2+ numbers to 9 in a row underneath, followed by 3+ numbers to 9. Then those were erased and replaced with 4, 5, and 6 + numbers to 9 for another month, etc.
Every time we did anything that required us to write on paper, we had to first copy all of the rows on the blackboard. After addition came subtraction in the same method.
Then in third grade, it was multiplication and division, but up to 12. Fouth grade was review, with 10 through 12 added to the addition and subtraction. Fifth grade was long division.
There was no mention of number sets or of prime numbers, just rote memorization.
So arithmetic was something I learned to do and to use when necessary, but it was boring. Math did not get interesting to me until we were introduced to elementary algebra in 9th grade.
mitch96
(13,907 posts)I still have a problem with multiplication tables.. Formulas? Those I can work with and use a calculator. Needed formulas for work and I loved my work so I made it work...
Math always gave me a brain cramp.. What everybody "got" I did not. For a while I though I was a product of some alien sperm that did not have a "math" gene...
m
wnylib
(21,479 posts)in math that he was like a human computer. My oldest brother was also a mathematical whiz all through school and into college. My younger sister started out as a math major in college because she was so good at it, but then got interested in sociology and switched majors.
That math gene skipped me. I did not hate it in school, but was bored with the way that arithmetic was taught in grade school so I tuned it out. In a family with 3 math whizzes, I felt inadequate in it. My good memory worked well in language study, which was much more interesting to me because of the variety of cultures that languages introduce people to.
But I did get more interested in math once I had algebra and geometry in high school. I later realized that I was not actually bad at math when I had a job that required me to do some quick, simple algebra and geometry calculations in my head. I just did not have the natural aptitude for math that other people I knew had.
My aptitude was languages and literature. So I majored in languages and minored in anthropology.
mitch96
(13,907 posts)Language always fascinated me. I had to learn a bit of spanish b/c of where I worked. Miami.
The nuances were a hoot. The same word in one country means or indicates something else in another country but it's still "Spanish"...I would have loved have taken a spanish language courses in different country's. Madrid, Mexico City, Ecuador.. I have been told I have a good ear for accents. A parrot.
Patients thought I was a native speaker b/c I spoke Spanish with a "cuban" accent... even though I sometimes did not know what I was saying.
I would get some words or phrases mixed up.. Like De Nada and De Nalgas..
Going to a foreign country, speaking the language and eating their food..
Really get to know them.. Now THAT would be a trip..
m
wnylib
(21,479 posts)Spanish was my major in college. I taught high school and middle school Spanish for a while, but most of my experience was teaching English to adult English language learners. The vast majority of them had Spanish as their native language. They were from all over Latin America - Puerto Rico, Mexico, Colombia, Ecuador, Venezuela, Costa Rica, Cuba, Dominican Republic, and Peru. One was Italian and had lived in Germany for a while. I guess that two languages, Italian and German, were his limit. He had a very hard time with English and kept putting Italian and German words and phrases into his English. One woman was Portuguese and her husband was Dutch.
Several of my students became personal friends after their classes were finished. They were homesick and a large group of them became each other's "family" away from home, with Spanish as a common denominator, despite the differences in accents, idioms, and some words. I was the "honorary Mexican" because they made up the largest number in the group and my vocabulary was more Mexican than any other form of Spanish.
We got together as a group for Christmas and birthdays, and in summer for picnics, plus other occasions like children's graduations, weddings, etc. Their church had mass in Spanish and a few times I went with them to a church event. One time the priest (from Colombia) asked me where I was from because my Spanish sounded "authentic" to him but he could not place the accent. I said, "Soy la gringa del grupo. Soy de Pennsylvania."
We have drifted apart over the years. Children are grown. Some people were transferred to other places in their jobs. A few have passed away. But at one point, we numbered about 30, plus spouses or boyfriends and children. When we went out for dinner (without the children) we took up 2 banquet tables, jabbering away in English, Spanish, and Spanglish.
There were some hilarious moments of misunderstanding, using a wrong word or phrase, them in English and me in Spanish. And some funny moments when they learned English words for things. For example, we had dinner at a Mexican friend's house who invited a newcomer from Mexico whose English was very limited at the time. The dessert was angel food cake. The newcomer said it was delicious and asked what it was called. She thought we were putting her on when we said angel food. So the hostess, also Mexican, pulled a devil's food cake mix out of the cupboard and told her that there is devil's food in America, too, but only for bad people. The look on the newcomer's face was priceless.
EYESORE 9001
(25,939 posts)Suffice to say, it was long ago.
skypilot
(8,854 posts)...the number 9 is the one thing I'm truly superstitious about. I won't go into all the history of it but I will not live in a house or apartment building where the numbers in the address add up to 9.
niyad
(113,323 posts)calimary
(81,298 posts)A trinity of trinities!
Skittles
(153,164 posts)a teacher in England who made math "fun", I loved it
packman
(16,296 posts)1x9=9
2x9= 1+8 (9)
3x9=2+7 (9)
and so on
to 9X9= 8+1 (9)
Backseat Driver
(4,392 posts)I found math puzzling and difficult.
Our elementary school was a guinea pig for the New Math - cheap paper mimeographed workbooks directly printed w/staple bindery out of the Yale printshop, I think. They weren't much into the tricks - used the long, involved processes instead of rules as I recall - endlessly circling 3 groups of 2 and 2 groups of 3 for proof they both equaled 6; thankfully, much modified since then...
Dear Bro learned to read by the whole word method; for him--not so good; he had a lot of problems. We learned phonics...
BigmanPigman
(51,607 posts)Also, if you put both hands out with fingers extended use the hands and fingers for the place of the digits. It only works for the "nines" though. My sister showed me this trick in my 30s! Why didn't she tell me this when I needed it in my own math class?!?
For example, 9 times 1...
Put down your pinky finger on your left hand for the ones place (9 times 1) and look at both hands. The left hand has 4 fingers and the right has 5 fingers so the place value is 4 plus 5 which is 9 for the "ones" place. Then for 9 times 2 put down the second from the left finger, the "2" on your left hand and you see 1 finger (place value 1) on the left of it and there are 3 more fingers to the right of it on the left hand and 5 on the right (3 plus 5 is 8). So you have "1" in the "tens" place and 8 in the "ones" place making "18".
Then for 9 times 3 do the same...put the third finger on your left hand down a d to the right of it you have 2 fingers and to the right you have 2 remaining up on the left hand and 5 on the right hand. The 2 fingers are the tens place of 2 and the remaining fingers are equal to 7 making it 27.
It is hard to explain and you really need the visuals. I taught this to my 1st graders and it empowered them with their older siblings who didn't know the trick.
I learned during my years teaching in elementary school that math is mainly patterns. It is all about patterns. Once you know this it makes math so much easier and even fun. The 1st graders actually loved math and their parents were amazed.
paleotn
(17,920 posts)Mathematics is full of wonderful symmetry. One of the things I've always loved about it.
3Hotdogs
(12,384 posts)and get to 20.
packman
(16,296 posts)3Hotdogs
(12,384 posts)packman
(16,296 posts)Your digits are truly legendary
3Hotdogs
(12,384 posts)now I'm blushing.
IcyPeas
(21,884 posts)iluvtennis
(19,861 posts)sarchasm
(1,012 posts)spike jones
(1,679 posts)Upthevibe
(8,051 posts)I don't think I've seen or known about this.
Thanks for the post
intrepidity
(7,302 posts)As for others above, arithmatic was taught as pure rote memorization. I never enjoyed math until geometry, because then I could visualize it. Many life/career decisions would later be based on this weak math foundation. Only much, much later in life (up to and including now) have I begun to learn to enjoy and appreciate math.
Grrrrrrr
Jimbo S
(2,958 posts)or a multiple of.