Post AXYIupx36akD3BAabw by macquilter@toot.community
(DIR) More posts by macquilter@toot.community
(DIR) Post #AXXNRgtnzJK3Bpc8Mi by grammargirl@zirk.us
2023-07-10T02:30:09Z
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OK, remember that I am a word person, and please don't mock me, but I learned something today about math that blew my mind.I mentioned to my husband I have always struggled with multiplying by 9. He countered that 9 is the easiest number.And I was all "No way, what are you talking about?" And then he told me these rules. 😲 There must be at least one or two other people who didn't know this and who will be as happy as I was to learn it!
(DIR) Post #AXXNk1nP26mpDEMZk0 by KimberlyN@mstdn.ca
2023-07-10T02:33:27Z
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@grammargirl Yes, that’s an oldie, but it made it easier for me too. Math is all about seeing the patterns in the numbers.
(DIR) Post #AXXO6BO43MvPKX4k0O by endocrine_witch@med-mastodon.com
2023-07-10T02:37:30Z
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@grammargirl did you also know about the trick to remember the multiplication table using your fingers? Here’s a cute video on it. https://youtu.be/_qmYcvChQwo
(DIR) Post #AXXOADx8SLWYRhPHNY by accessamy@mstdn.social
2023-07-10T02:38:14Z
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@grammargirl One of the best things I ever learned! (But when I get to 9x12 my head explodes a little and I feel even less smart. 🥴 )
(DIR) Post #AXXOY2ifsAZ2YZ05Oi by pmb@universeodon.com
2023-07-10T02:42:34Z
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@grammargirl Do you know the ×11 rule? Add the two numbers together and put the result in the middle of the number you’re multiplying. For example, 15×11= 1 (1+5) 5 = 165
(DIR) Post #AXXQ1GWrhxoXjoyWEy by Daniel_Loxton@sauropods.win
2023-07-10T02:59:01Z
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@grammargirl I always used this short cut pattern: 7 x 9 = 70 - 7 = 63
(DIR) Post #AXXQ6ZUmcQdQ0dX0Ai by Freedom2B@kolektiva.social
2023-07-10T02:59:55Z
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@grammargirl Confused. I like my table. 🙂
(DIR) Post #AXXQIOI26gyIjMCfZ2 by USelaine@mastodon.online
2023-07-10T03:02:04Z
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@grammargirl That’s the only way I can remember.
(DIR) Post #AXXQrXUns4uVPxw8US by grammargirl@zirk.us
2023-07-10T03:08:29Z
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@pmb I didn't know that either! Thanks.
(DIR) Post #AXXR3sNq2Mt9ftYsLI by grammargirl@zirk.us
2023-07-10T03:10:44Z
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@endocrine_witch I had never seen that before either. Amazing. (At this point I'm wondering what was wrong with my school!)
(DIR) Post #AXXRYuV8DJvhDflrpQ by pmb@universeodon.com
2023-07-10T03:16:21Z
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@grammargirl You’re welcome! Math and language a killer combo 🤓
(DIR) Post #AXXRciQL3iK4v9LN7g by dernub@universeodon.com
2023-07-10T03:17:02Z
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@grammargirl If you look at the pattern, you’ll see the 10’s digit going up, 1 - 8 (if only going 9x9) and the 1’s digit going down, 8 - 1.
(DIR) Post #AXXSfHdXD2OIfHIvwm by mlanger@mastodon.world
2023-07-10T03:28:41Z
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@grammargirl Here’s a related trick related to transpositional adding errors. Suppose you want to add 316+214 and by mistake you add 316+ 124. The 124 is a transpositional error because two digits are swapped. The difference between the correct sum and the sum with the transpositional error will always be evenly divisible by nine. In this example: 530-440=90, 90/9=10.Try it!And it is possible to be a word person and a numbers person. 😉
(DIR) Post #AXXTP58Y115BDaeHwG by kagan@wandering.shop
2023-07-10T03:36:53Z
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@grammargirl I knew this already, but I'm not here to mock. You, and the others who are about to (or just did) learn it from your boost, are in today's Ten Thousand:https://xkcd.com/1053/
(DIR) Post #AXXUckuc6hqCV6DPdI by glightly@mastodon.social
2023-07-10T03:50:39Z
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@grammargirl It is helpful!I learned things this way (I'm that old). https://www.youtube.com/watch?v=2BgYGHsW8fY
(DIR) Post #AXXVT7UfOXOdau32UC by endocrine_witch@med-mastodon.com
2023-07-10T04:00:04Z
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@grammargirl Sadly it only works for 9 :) there's more complex finger math for the other numbers... which I no longer remember.
(DIR) Post #AXXWvmEjbfYI1EpBXk by PamelaBarroway@mstdn.social
2023-07-10T04:16:28Z
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@grammargirl I recall my practicing times tables with my dad in 3rd grade — which for me was 1973. He wrote down every single one on its own index card: 5x2=10, 5x3=15, and so on. After dinner he’d help me memorize those index cards. First in order, then mixed up, until I had them down pat. Today I can recite them perfectly from memory. Is it the optimal way to learn multiplication tables? Probably not, but I sure do know them … and I have a lovely, lasting memory about my father.
(DIR) Post #AXXYPvXjfaJdWYeWp6 by zkarj@mastodon.nz
2023-07-10T04:33:06Z
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@grammargirl here's another trick for 9s… AND 11s.1/9 = .11 11 112/9 = .22 22 223/9 = .33 33 33etc1/11 = .09 09 092/11 = .18 18 183/11 = .27 27 27etcI.e. the decimal digits of 9ths are multiples of 11 and vice versa.
(DIR) Post #AXXbrXoJnevvtEGmOm by happmacdonald@retrochat.online
2023-07-10T05:11:44Z
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@grammargirl https://www.youtube.com/watch?v=-WOgLltWhggAlso I made a multiplication table practice webpage doodad for mah kiddos that I was proud of, and that they actually tried more than one time apiece xDhttps://lightsecond.com/MultiplicationTable/
(DIR) Post #AXXdCQswqL8mRkxXaS by RubyGloomIRL@bluejay.social
2023-07-10T05:26:44Z
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@grammargirl @ElizabethLeeCo cool. I learned to multiply 9 (1-10) on my fingers. Holding up both hands, palms facing you, fold down your right thumb, 9 fingers still up. Fold down only right pointer finger, thumb and eight fingers. Left pinky down (6x9) 5 up, space, 4 up.
(DIR) Post #AXXlD5KbGVKLWMiPgm by DarlavdRiet@mastodon.nl
2023-07-10T06:56:29Z
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@grammargirl I’m as amazed as you are! I didn’t learn this in school, either.
(DIR) Post #AXXmyRiRxOxiVi1CAC by kofanchen@drosophila.social
2023-07-10T07:16:12Z
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@grammargirl I didnot know until this post! Amazing
(DIR) Post #AXY0tgVCx8byHQRqbI by Elddawt@mstdn.social
2023-07-10T09:52:14Z
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@grammargirl Thank you. I'm hopeless in this area any tips welcome.
(DIR) Post #AXY0xheibfAd11oSUi by TerryBernstein@ohai.social
2023-07-10T09:52:58Z
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@grammargirl That never worked for me. Those kinds of rules never seem to stick in my head when they're needed. But simplifying does.(Times by 10 then take the number away; so 7x9 is "7x10 then take a 7 off").
(DIR) Post #AXY2G5phYTMTANHbZA by virtuosew@mathstodon.xyz
2023-07-10T10:07:30Z
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@grammargirl I so wish my school had taught us about this! As it was they were in a phase of not really even doing times tables, and they never even mentioned number bonds - my Mam had to show me those, and chant times tables with me on the way to school.I sometimes think that the whole idea of maths education in the seventies was to make it harder, and remove all aids.And yet every mathematician I know has a whole array of tricks and shortcuts, and uses them All The Time!
(DIR) Post #AXY3FFI90BeuAOkLiq by Galley@mastodon.online
2023-07-10T10:18:27Z
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@grammargirl OK, so the second part was probably known at the time, but I’m pretty sure I discovered the first part (in 1980). 🤓
(DIR) Post #AXY8C3TsxNaeRGXJwG by statesdj@genomic.social
2023-07-10T11:13:59Z
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@grammargirl Q: Is a number divisible by 9? A: Do the digits add up to 9Q: Divisible by 3?A: Do the digits add up to 3Q: Divisible by 2, 5 or 10?A: You only need to look at the last digitQ: Divisible by 4?A: Last digit, and is the 2nd to last odd or evenQ: Divisible by 6?A: Is it divisible by 2 & 3Oh 7 and 11, there are rules, but they're too complicated. Easier to just remember.Numbers are fun :)
(DIR) Post #AXY911syeDHIGAZylc by opal@ioc.exchange
2023-07-10T11:22:59Z
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@grammargirl Even cooler: this pattern applies to other number systems (bases), too!One other fun thing: you can use this rule to check if a number is divisble by 9. Just add up the digits, and see if it's divisible by 9.For instance: 3312 is divisible by 9 because 3+3+1+2=9. 5166 is divisible by 9 because 5+1+6+6=18, and 1+8=9.It's a really cool rule!
(DIR) Post #AXYIupx36akD3BAabw by macquilter@toot.community
2023-07-10T13:14:05Z
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@grammargirl I learned this trick decades ago and wish it were taught in schools -- it makes it so much easier! I taught it to my children and grandchildren, too.
(DIR) Post #AXYO2zb7ck353Ucc5Y by grammargirl@zirk.us
2023-07-10T14:11:38Z
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@pmb I didn't know the x11 rule either!
(DIR) Post #AXYOZsXks9tSjVjDQO by grammargirl@zirk.us
2023-07-10T14:17:33Z
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@virtuosew At my school we just memorized times tables.
(DIR) Post #AXYP0luPeDWHyW9Lg8 by grammargirl@zirk.us
2023-07-10T14:22:24Z
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@zkarj Wow!
(DIR) Post #AXYPJ95oBoPR5hF24e by grammargirl@zirk.us
2023-07-10T14:25:47Z
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@glightly Wild. I loved Schoolhouse Rock, but I don't remember that one.
(DIR) Post #AXYSuOgDV0c20jj2w4 by virtuosew@mathstodon.xyz
2023-07-10T15:06:03Z
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@grammargirl That was Old Fashioned Rote Learning and was very much not a thing. I wish it had been, not least as memory training!
(DIR) Post #AXYWNwmK6I9U1fMcqG by Storrieville@mastodon.social
2023-07-10T15:44:58Z
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@grammargirl I was completely unaware of this!
(DIR) Post #AXYtA9DzKKWZWDh1ma by Aviva_Gary@noc.social
2023-07-10T20:00:11Z
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@grammargirl Neat... I know a couple of the ones in thread but if you find it I am looking for the multiplication one where you draw the lines and count the intersections for the numbers like 101x 27 or something...(I saw it on a vid once but never learned it in school)
(DIR) Post #AXYv3RtZi8gXJ34vD6 by mikej@mastodon.online
2023-07-10T20:21:28Z
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@grammargirl I came up with that myself in elementary school and was told it was way more work than just memorizing without thinking about it. Which was why I hated math until I got a Commodore 64 which let me do weird stuff without saying that was a dumb way to do it.
(DIR) Post #AXeshH5VEIpYlJSU8e by willmore@twit.social
2023-07-13T17:21:09Z
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@grammargirl I used to teach this rule to students when I was helping a teacher by adding enriching activities. I use a visual description where you hold up you ten fingers and count over from the left how many "nines" you need to multiply by. For example, to multiply 1x9 you would drop the leftmost finger and be left with 9 fingers on the right. For 2x9 you would drop the second from the left finger and be left with 1 finger on the left and 8 on the right. They loved it.