Does mental arithmetic add up in a world of calculators?

Comments

13 March 2013

You don’t even need a piece of paper and a pencil for that one! I often do the 13x and 14x tables upto nineteen [above that number I would probably split the multiplication and add the results], and sometimes I see how far I can get adding up three columns simultaneously and doing long division in my head. I usually add up the cost of purchases in a shop so that I can give the right money and I have a rather un-amusing tendency to say “Correct!” when the assistant tells me the total. I enjoy arithmetic but I am no mathemetician.Trigonometry defeated me and I never mastered the slide rule.

william says:

13 March 2013

Without the ability to use your own grey matter, know can anyone be confident that they even typed in the numbers right ?

And as John described above I split the numbers multiply x 2 store, start again by multipling by 3 , multiply that by another 10 look at the answers, select one.

wavechange says:

13 March 2013

For me the simplest way of calculating 27 x 32 is to add together the products of 27 x 30 and 27 x 2.

I used to add up the price of my shopping, like John, when Tesco used to give vouchers if you spent more than a certain amount, though there was the cost of loose fruit & veg to be added when these were weighed at the till.

Using a slide rule was what gave me more confidence with numbers than anything else because it is necessary to do an approximate calculation to decide where to put the decimal point.

My first calculator was a Sinclair Cambridge, bought as a kit for £24.95 plus VAT. I used this a great deal when I was doing my PhD. The components had to be soldered to a circuit board. I still have the calculator and the stabilised power supply that I made to avoid the high cost of batteries. The calculator did not have a Pi key but the instructions said that Pi could be calculated by dividing 35500001 by 11300001. Useful but definitely not up to Gareth’s standard.

While working in university I tried to encourage undergraduate and postgraduate science students to handle numbers without using calculators but soon gave up and focused on helping them gain confidence with numbers with the aid of their calculator. At one time, many Greek students could do mental arithmetic and I was told that they were not allowed to use calculators at school.

I can’t say I enjoyed maths, though it is very handy to be able to do basic mental arithmetic.

william says:

14 March 2013

You mean you can’t quote pi to a silly no. of dp from memory ? 3.1415926535 I used to be able to include 8979 on the end

And I can still roughly remember the square roots of 2 (1.41) and 3 (1.7) although not to the same number of dp I could do and 5 was just not even close. Why 30+ years on I can still remember them I’ll never know.

I used to write silly programs to run on things like ARPANET (if anyone can remember that) and was impressed when 1000! (I’d like to put 1000000! but I’m having a hard time believing that now) was computed in under 2 secs on one machine I found ( with all the digits). Don’t think I could manage to write that one know though.

I don’t use calculators anymore, I’ve moved onto spreadsheets, although I’m aware that some well known versions have got their sums wrong in the past.

Argonaut... says:

14 March 2013

Calculators were not allowed in school exams in my days.

I did and enjoyed maths up to A level and use quick maths
calculations all the time at supermarkets.

Try multiply 55 by 55 or 65 by 65 or indeed 95 by 95 that can
all be done instantly at one go w/out splitting anything.

Got it?

wavechange says:

14 March 2013

On that basis, Pi rounds to 3.1415926536 🙂

Like William, I can remember all sorts of numbers, including those that I used to use when I was at school and university. Log to the base 10 of 2 is 0.3010, log of 273 and 760 (STP temperature and pressure) are 2.4362 and 2.8808, and so on. Perhaps if my brain was not clogged with numbers and how to do calculations I might remember people’s names for more than five minutes. 🙁

Malcolm R says:

14 March 2013

I worked with someone who used his calculator all the time – even when dividing by 2 (that sticks in my mind). Mental arithmetic is a habit, and one well worth practising. Out shopping to decide the cheapest option, calculating quantities for decorating, measuring for carpets to get an idea of cost, estimating mpg (litres/100km if you’d rather) and lots of other examples where you wouldn’t have a calculator.
There are lots of short cuts we learned at school; I bet they don’t teach them now.

wavechange says:

14 March 2013

Those who don’t do mental arithmetic are likely to have a phone with a calculator – wherever they go. To start with, phone calculators were pathetic things that did not recognise algebraic priority but modern offerings are more sophisticated.

Rosie O'Hara says:

14 March 2013

Without the basics of mental maths we are stuck, I was stuck for many years, I had some incredibly good strategies to get round what I couldn’t do.
I’m currently researching how people do mental maths to produce an NLP Model to teach children effectively. I now know the basics and I used those to do the sum above correctly 12 years agao i could not have done that (I possess a free bus pass now by the way)

Patrick Steen says:

14 March 2013

If you have any good tips, please share. I think the Trachtenberg system is interesting. Anyone else use it? http://en.wikipedia.org/wiki/Trachtenberg_system

Ian Addison says:

19 March 2013

There used to be a thing called arithmetic which was seen as separate from mathematics but everyone knew it was a required basic grounding. Its focus was the use of “arithmetic ” in every day uses. Adding up bills, calculating how much paint, distance , miles per hour , sailing times, bank interest compound and simple, stocks and shares, currency exchange. It even had its own higher (yes I am Scottish). This concept seems to have disappeared. I think it is a great pity as folks seem to only talk about mathematics and that puts folk off (oh I like mathematics ) and I can understand why.

Ian Addison says:

19 March 2013

oops i meant “o” level

Rosie O'Hara says:

19 March 2013

It’s called Maths or Mathematics at school at all levels in Scotland, which is the area in which are located and working predominantly.
(It was arithmetic in my day – I still couldn’t do it.)

Clint Kirk says:

Sum of us need calculators

The cushion of the calculator

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