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?
-
Look at the edit history if you want a laugh.
@futurebird that's the mistake the lab rats made when they built the earth
-
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@sauropods.win What base are we working in?
-
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 This for me changed over the years. At first I just remembered the answer, but after not doing mental math for a while I'd forget. My first shortcut was (8 * 5) + (2 * 8), I learned from a school friend. Later I also learned (7 * 10) - (7 * 2). As I got more familiar with binary, powers of 2 became more intuitive so I also tried (8 *
- 8. But these little tricks are mostly not needed, with a little practice everything comes back, and I revert to memorizing the result again. -
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 mostly directly, but sometimes by comparing it to 7*6 or 8*8
-
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 Because I know 7 x 7 is 49, I just add another 7.
️ -
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 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.
-
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 Numbers below about 200 form a grid of products in my head because I've been thinking about number theory and discrete factorization for nearly 40 years, so for me 7*8 being 56 is just like, duh, what else would it be.
-
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 7x8 was the only one under 11 that didn't just seem self-evident to 3rd-grade me, so I had to memorize it. It still doesn't have an image or feel for me the way the rest of the 0-10 times tables do...
-
@kbm0 @futurebird we went up to 10*10 in West Germany.
We also memorised up to 12 x 12 despite being a country that uses the metric system.
-
@futurebird I have the weirdest thing with this.
When I had to learn those multiplications my mom would question me for practice. I always forgot the answer to 7*8.
One day we were in the living room and the TV remote was on the table. Remember the numbers on that:
1 2 3
4 5 6
7 8 9So I saw 7 and 8 on there, and the right answer just above. It clicked in my head.
So whenever I have to multiply 7 and 8 I see a TV Remote in my head. We don't even own a TV, I havn't had one since 2001.
@johnnythan @futurebird that’s actually really cool! Crazy how the brain works sometimes.
-
@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 that's 7*7
-
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?
Usually 8x8=64-8=56
Sometimes I just grab my phone or calculator.
In lab, it’s always the calculator cause I’m not messing up a week of experiments because some internalized bully says I should be able to do that in my head.
Something I try to impress upon my undergrads, if there is any possibility that you’ve done a calculation wrong, check it with a calculator.
-
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 Had to memorise all the tables up to and including 12, so that’s why it’s just retrieved from my memory - must say it’s kinda useful though. I had also attempted to do up to 16, so I can recall the 16 table (due to CS) but I’m a bit spotty on 13-15
-
@futurebird I think “7 times 8 is 56” because for some reason that’s how I memorized the multiplication tables. Almost got me in trouble with the other third graders in a “multiplication bee” where I was destroying them but whispering the first part under my breath.
Those fucking records.
-
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
It used to be instant, but now I have to think about it. I have no instant way of checking. -
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 for that sort of big math problem, I'll use the sliderule. (although since 7 times 8 would overflow, you have to use the log(7) - (log(10) - log(8)) technique to find the answer of 5.6 times ten to the something)
-
@futurebird I have the weirdest thing with this.
When I had to learn those multiplications my mom would question me for practice. I always forgot the answer to 7*8.
One day we were in the living room and the TV remote was on the table. Remember the numbers on that:
1 2 3
4 5 6
7 8 9So I saw 7 and 8 on there, and the right answer just above. It clicked in my head.
So whenever I have to multiply 7 and 8 I see a TV Remote in my head. We don't even own a TV, I havn't had one since 2001.
We had some paving stones laid in our back yard.
Two guys did it. I was about 8 years old.
They were figuring out how many they needed to do the yard.
One said, in an Irish accent "Five eights are forty, eight covers are forty, whichever way you look at it, it's forty slabs".
I've never forgotten both the result and that multiplication is commutative.
-
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 usually manage to remember the small factors (2 or 3) and 5×. So 7×8 = (5×8) + (2×8). I was never very good at remembering the table, and I was glad when I understood the intuition of which known numbers I could add up/subtract.
In elementary school, I thought I was bad at maths because I just couldn't remember those numbers well, now I have a PhD in physics... -
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*8 = 7*2*2*2 = 56.
This is a useful “trick” that allows you to break down many calculations into simpler parts.
-
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 still remember it as 8*7=56, which is easy because of the way we say numbers above 20 in Dutch.
"Eight times seven is six-and-fifty", 8 7 6 5.
