How do you do mental math?

Nachum Pereferkovich asked 1 year ago
1187 views 4 comments

I got the feeling that some kind of connection exists. All the mathematical calculations in my head I do only with the help of words. Under such conditions, to correctly copy the 10-digit phone number manually from the monitor onto paper, it takes me at least 19 seconds. Clearly, math is not my forte. But could it become my forte… what other ways are there to do “mental math” without visualization?

How do you do mental math? Share your experiences in the comments below.

Reg Forsaith November 21, 2019 01:16 pm

When I was younger, it was pretty easy and I don’t know how I did it.

Not "savant level cube root of poly digit stuff, but simple arythmetic was no big deal.

Now I’m older, I often resort to breaking things into tens, hundreds etc, or nearby multiples


8, 2,3,7,6,4 added up get broken into the three pairs that make up tens,and there’s three of ’em, so thirty.

25% discount off of $47 is well nearly $48, so a bit less than $12. If I then need to get picky, well its $1 less and that’s $0.25 so$11.75 discount

That sort of thing.

These days, I’m more likely to just reach for the phone and select the calculator app.

Its never seemed to be a visual thing, just a practice thing.

Like I can still recognise integral calculus, and I understand the principle of it relating to an area under a curve, but couldn’t solve one to save my life.

Iblis Bane replied 1 year ago

Yeah, that’s pretty much how I do it. Break it into easy round-number sums, (often multiple ones) and then do the last minute adding or subtracting for the differences.

dusti foster January 27, 2020 04:13 am

I can do mental math, but if I use my fingers it is easier and faster. I took a lot of flak for that at school, though I never understood why.

Dianna Moylan February 21, 2020 06:53 pm

I was really good at mental maths as a child and continue to be so. How would pictures improve this, i wonder. I think they’d just get in the way.

Dax October 31, 2020 12:32 pm

hmmm – by math do you mean arithmetic and manipulation of numbers?

Asking becausing there is a lot more to maths, I have a degree in pure mathematics and can bore most people to death discussing infinity, countable sets and other amazing concepts. Had plenty of subjects where there were no numbers or arithmetic. The more abstract the better!

Simple arithmetic is often just manipulating numbers and memorising rules and tables. My addition and multiplication tables are words i say back. Like i remember song lyrics. Not the sounds, just memorised the words but also like a "pacing" to how imsay them back.

Rules, algorithms, procedures, my brain is good at remembering. So I can just apply them.

Im not bad a sequences of numbers, they just stick. Probably better than names. A few weeks ago was at a mechanics picking up my car when a couple came in, the mechanic told them about their error code and then had a few minute discussion. At the end he said "and the code…", he paused while trying to remember it, I just repeated the code back. The couple looked at me and i said "Im good with numbers". A few days later I was at the supermarket and they were there. They looked at me and I could see they recognised me but couldnt place me – I told them "at the mechanics – code P0154". They were shocked and said yes you are good at numbers. BTW that was 2 months ago and I still have the error code stuck in my head. Just googled it (busted oxygen sensor) and only now remembered what the mechanic said about the busted sensor.

Can remember phone numbers from my teen years. Friends university ids, 7 digit numbers.

I did find that at university that I was better at some geometric stuff than my friends. They would visualise it, while I would "conceptualise it". It meant i could handle some things in 4 or more dimensions, where they couldnt see it as it couldnt be done as a simple visual.

And yes, I am wild fun at parties.

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