When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
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@johnnythan @futurebird Similarly, when I have to tell left from right, I think of my the last turn when driving to our local library when I was an infant, because I'd overheard an adult call it a left turn. I _see_ that road every time. I'm 49.
@KennyPark @johnnythan @futurebird
To be absolutely certain about left vs. right, I start to pick up an imaginary pair of scissors. I know I use my right hand to do that.
I found that 'trick' in like 1st grade. I have since worked in jobs that use analytic geometry and multi-variable calculus. I have debugged issues arising from using a left-handed coordinate system instead of the standard right-handed one. I still have to reach for the scissors.
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@futurebird
7*8 in particular, I have to work out. I'd probably go 70 (7*10) less 14 (7*2, to get to tines
to get to 56. For many other pairs I have tricks already memorized, shortcuts to look up the right answer.
I used to just completely not know it and have to do complicated addition or subtraction. But since my kid's 3rd grade teacher told their class "I am 56 and so you just remember that 7x8 is my age you'll get there... also 5 and 6 come before 7 and 8... so you can remember that," and my kid told me and now I've got it memorized.
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@futurebird For some reason I developed a HATRED for rote memorization of times tables in school. As long as I understood the concepts of how to multiply, why did I have to memorize so many answers, and calculators already existed and were clearly going to become cheaper and more common, and if I didn't have one I could figure it out in a minute anyways.
There is a flip side to this you may not be aware of.
I have Dyscalculia. The numbers version of Dyslexia. I find it incredibly difficult to add, subtract, multiply, and divide.
Without the rote learning of the times tables back whilst on the Ark, it would take me a very long time to work out that 7 x 8 is 56.
As for calculators, you'd be surprised by the absolute hassle it is to get out a calculator when you sometimes have to do it multiple times a day. Numbers and the need to utilize them is literally everywhere. Just like words are for the Dyslexic.
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
I have dyscalculia; rote learning the tables is the only reason I can come up with the answer instantly.
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It's worth pointing out that I wasn't 'taught' this method by anyone... I simply discovered it naturally and started using it.
@Anomnomnomaly @futurebird There are multiple levels of meta when you say "i learned" or "i was taught" or "i figured out [by my own device]. The processes behind is what creates the magick of a human intellect. There is NO 10-point list for that. None of us got something from g#d that made us better/cooler/smarter than the next guy. It's just luck (Quoring: Joni Mitchell & Chalie Mingus, Dry Cleaner from Des Moines).
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
Mostly I have that one memorized. Otherwise, I decompose it into 5*8 + 2*8, which is 40 + 16.
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Look at the edit history if you want a laugh.
If that's how your brain is working this morning, I recommend you don't play around with 57 just now:
https://hsm.stackexchange.com/questions/6358/story-of-grothendiecks-prime-number
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
The bigger question is: are the hardest ones 6*7, 7*8, and 8*9 just for me, or for most people? And why?
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
@futurebird I think that I get the answer because treadmills get set at 7.5 mph to get 8 minute miles. Maybe my answer should be “another math trick.”
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
@futurebird I don't instantly know what 7*8 is, but I do know what 8*7 is.
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
I have a lot of anchor points in the times table memorized and 7*7 and 8*8 are two of them. I use them to get to the close by result quickly
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
8×8-8
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
@futurebird 7*7=49 + 7= 56
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Mostly I have that one memorized. Otherwise, I decompose it into 5*8 + 2*8, which is 40 + 16.
@michael_w_busch @futurebird Yup, same. Alas, I don't have the full* table memorized these days, but I know enough to be dangerous and can 2-step my way to the answer.
* Did we all learn up to 12x12? That's how UK schools do/did it.
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
@futurebird 4*14, maybe?
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
@futurebird
Memorized, sure, but that particular product takes me a second to remember it. -
When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
ohk im happy with the poll result, im also one of those that have some basic math thingies memorized and not really do any math to figure it out... phew!
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
@futurebird I will admit to doing 7×7 in my head and then adding seven!
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@futurebird I did 7*7=49 then added 7, which means 1 less than 7+50 (because ending in 9), resulting in 56.
I did have the multiplication tables memorized in 3 & 4 grade, but I don't really much basic math on a daily basis, and if I do, I generally need to write it down so I can see it. I'm afraid that if I don't make a deliberate effort, I'll be innumerate.
28*2 or 50-14 probably.
Rote - instant recall - memorization of the entire table seems unnecessary to me… once the first half is in your head the rest is available quickly though doubling and adjacent addition/subtraction, but also, because human brains are very inconsistent at it. Personally, I think that flexibility of knowing how to connect relationships across categories and patterns is a huge part of learning to *think* mathematically.
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When you need to multiply 7*8 do you simply have it memorized, or do you need to add, subtract or otherwise connect it to another math fact that you know better?
That is do you simply think "56" or are there more thoughts that lead to 56?
@futurebird I would say I don’t have it memorized. With the explanation given, I’ll probably use the other math fact that I have 2**n memorized a bit. So 8**2 = 64 then 64-8 = 56.
