For me it's 8+8-1 since the doubles are memorized
this post was submitted on 01 Oct 2025
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This is the same for me, but I did 7+7+1, basically
So, for me it is 10-8=2. Then 7-2=5. And then 10+5=15.
In high school calc, I would do all kinds of algebra, integration, etc. and then at the end add 8 and 7 and get 13. All the time.
Its like when you do the whole logic and calculations part and then forget to square root the number at the end.
I'd always forgot to change signs after multiplying
Must have been doing a lot of base-12 math?
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I am an accountant, literally work all day with numbers. 8+7, fine, that's 16 minus one or 14 plus one.
8x7? Never managed to memorize the times tables so that is, well 4 7s is 14 +14, that's 28, so 8 7s is 28 + 28, which is 40 and 16 so that's 56.
interesting how mathes works differently for many people. because I do 8+2 to get 10. then 7-2=5, so 10+5 = 15.
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Quick mafs
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I don't know what to make of this comments section. This many people really don't have 8+7 down?
I don't even feel superior about it, just bewildered.
Yeah, I thought there was something more to it and am disappointed.
Maybe I just have it fresher in my head because I play a lot of Killer Sudoku. 15 pair box? That’s a 7-8 or a 6-9.
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In my case, the mental math trick suggestion (make it 10 + 5) was intended as a way to build a skill using the provided, easy example. That type of mental math can be applied to much larger numbers, particularly when combined with other mental math tricks.
For us older folk, and unfortunately, also for some younger folk that grew up in more "conservative" small towns, borrowing and fancy math trickery was the work of the devil.
We were required to memorize the addition tables as well as the multiplication tables. And even then, addition could be done on your fingers and toes so as long as you could add the big numbers like 8 & 7 together faster than the really slow kid could take off his shoes and work it the hard way, you were considered proficient at addition.
So ya, there's a wide swath of America that just sucks at basic math.
This is why learning binary is so important. In base two, the same equasion is 1000+0111=1111, now you just convert back to decimal with: 8+4+2+1= sweats and starts counting on fingers before reaching for calculator
Easy, just convert to hex, 0x0F
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Mental math tricks are important.
Take 2 from the 7 and give it to the 8. You now have 10 + 5. Much easier math.
Take 2 from the 7
Hold on, I just need to check something. Looks around nervously
Yes, that seems easier to me as well! I was not allowed to do this according to the teacher when I was a child. They wanted me to do it in some weird counterintuitive way. But I was very stubborn and I am still doing calculations in this way. She is not the boss of the way I think!
8+7 = 8 + ( 2 + 5) = ( 8 + 2 ) + 5 = 10 + 5
Then just do the column addition (1 + 0) =1 and (0+5)=5
Thus concat(1,5) = 15
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Okay I know it's 15, simple math, after all 8+8 is 16, you would have to be an idiot not to know that, so it's just 1 less than that, anyways let me pull out my calculator just to check...
I once typed in 1+1, though it was several term equation and I was mentally reducing each term before punching it in.
I am chronicly paranoid because I have had a low battery on an exam. I just type in simple math because it might be totally borked and you won't catch it on something complex
Wait, it gets things wrong on low battery?
It...shouldn't. The 7-segment displays will have contrast issues, then the whole thing will stop working entirely when the battery gets too low.
I can't speak for low battery, but I can for different brands of calcs.
Back in high school majority of students had this specific model, and I had a different one. My entire answer to a question on an exam was correct, but my calculator somehow calculated different decimals to the ones from the popular model. And it was like 4th, 5th decimal or something. The asshole teacher took all of my points away on that. Meanwhile, one of her fave students forgot a very important part of the formula which made the calculation completely wrong and the teacher still gave them half the points for it. God, I hated school, lol.
Same. In contexts where there are a lot of already taxing elements, there is just no mental bandwidth for switching gears and doing the calculations. So calculator it is. I do find it important to hone my skills from time to time, just not to lose them.
When I'm doing woodworking and I need to add up some very simple measurements I always use a calculator. I could very easily do it in my head and often automatically do without even thinking about it. However I've learned the hard way it's very easy to make a simple error with even something as simple as 8+7 and chances are you won't find out till later when two parts don't fit together. That's 20 hours down the toilet, just because I didn't double check using the shop calculator.
I'm alright when it comes ro mathematics, but my memory is a swiss cheese. I'll do a calculation, context switch and 3 seconds later it's either gone or I remember incorrectly. Having things written down, on paper or in a calculator, gives peace of mind.
Totally this. Find an online calc that accepts fractions and just get it done right in a few seconds vs trying to convert to 16ths or some crap. Which is why I use all metric unless I’m forced into imperial units.
oh i know that one from my cribbage days
Why? Just take the time to do the work properly. You will get better at it, enjoy life more.
My thought exactly. I resonate with this meme but I also try to challenge myself to do math longhand on paper
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Why would you just type 15 into your calculator?
Like semantic satiation, where you say/hear a word so much it stops making sense, is there one for numbers? Permutation satiation? Trying to do basic, easy mathematical tasks and the numbers stop making sense and begin slipping away.
Don't you just carry the 1?
No, it’s Carry On My Wayward Son.
I actually never learned this (terrible math skills from never learning basics)
Is that just adding 7+7 and then 1?
I was just being dumb.
But 8-7 DOES leave you with 1. And if you carry that 1...well. You get the picture. The possibilities are endless.
I can barely carry myself, don't expect me to carry numbers.
15
I just say I'm not good at math while i look at someone in the eyes for a little while until they do the math.
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