Does mental arithmetic add up in a world of calculators?

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.

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?

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.

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.

oops i meant “o” level

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.)

Without any, even basic mental arithmetic skills, many people would even struggle to do that. And yes 2 x 7 ends in 4 so that leaves just 2 possible answers. Nothing wrong with that, its still mental arithmetic

This shows the dubious value of multiple-choice answers. It isn’t mental arithmetic to decide it ends in 4, and therefore you can choose between two answers – that is more logic. Mental arithmetic is working the answer out without any clues.

I agree, Malcolm. It would be better if the we could type in our answer and be told whether it is right or wrong, plus the percentage of correct answers submitted. Even if the website was capable of doing this, some people would cheat and use a calculator.

Maybe even enter your answer, then enter your method of calculating it, mental, calculator, spreadsheet, smart phone etc, to see how many people who use gadgets still get the answer wrong.

6

Oh sorry, 321 + 321 = 642 double that 1284 add 321 = 1605 ; So that’s 5 times and still a bit more to go

1782 – 1605 = 177, which is more than half 321 hence 6

6 rounding up. 5 x 321=1605. 1782-1605=177 – more than 1/2 of 321 so nearer 6.

I calculated 5 x 321 and 6 x 321 and wrote down the answers: 1605 and 1926, respectively. The latter is closer to 1782, so the answer is 6.

1024. It’s just 256 x 4. Double 256 twice gives 1024.

Next time I go shopping I will look for a real example of the need to do mental arithmetic to compare unit price of individual items and multi-buys.

6×300=1800
5×300=1500

6 is closest to 1782 Qed.

franjam, it hasn’t taken you 8 days to do this, has it? (Just teasing!)