ali

1274816. Sun Feb 18, 2018 4:41 pm 


The only thing I can think of is that it may be pedagogically useful. Students will (I assume) be familiar with powers of 10 and scientific notation before moving on to logarithms, so base 10 logs would be a natural first step. I don't know  I learned logs for doing hard sums back in the dark ages. 




suze

1274817. Sun Feb 18, 2018 5:23 pm 


Jenny wrote:  I am fairly confident that when I was in what is now called Y6 in 1960/1 I was taught long multiplication and quite possibly long division. I didn't encounter decimals and logarithms until I was in Y7 though. 
I first encountered decimals in about Grade 3 (Year 4). But while I was of course aware of fractions like one half and three quarters much earlier, I wasn't taught how to do arithmetic with them until junior high, so Grade 6 (Year 7).
I didn't encounter logarithms at all until Grade 11 (Lower Sixth), but we had calculators by then and we were never shown how to use logarithms for hard arithmetic since we didn't need to do it. My dad knew how to do it, and once at a parents' evening he spent some time talking at cross purposes with my Math teacher because the teacher considered logarithms to be natural by default while my dad considered them to be base 10 by default.
The good husband knows how to do hard arithmetic on a slide rule, but only because his grandfather gave him one when he was about eight. He doesn't think he ever used a slide rule at school, and I certainly didn't. 




Spud McLaren

1274819. Sun Feb 18, 2018 5:48 pm 


I still have the slide rule I bought in a deal organised by my school (electronic calculators were hideously unreliable, expensive and difficult to operate) and have actually used it for a short period professionally.
I also have a planimeter (an instrument used for finding the area of an irregular plot from a scale map), also obsolete because computers now do it quicker and more accurately. I probably couldn't remember how to use either of them now. 




Alfred E Neuman

1274822. Sun Feb 18, 2018 6:18 pm 


I used a slide rule at school, because I could. I was one of two who knew how to use one, and we were geeky enough to use them even though we didn't actually need them  the guys who might have benefitted from some mechanical help didn't have a clue how they work. Calculators weren't allowed in class, but slide rules were. 




Spud McLaren

1274823. Sun Feb 18, 2018 7:27 pm 


GuyBarry wrote:  What is the purpose of common logarithms on calculators?... the sole purpose of common logarithms, before the calculator was invented, was to enable people to do multiplication and division and to work out powers and roots. The invention of the calculator, and specifically the scientific calculator, made common logarithms redundant. So what's the button doing on there?  I'm told that all sorts of scientific and engineering operations use base 10 logs, notably analogue electronics. My wife's brotherinlaw works for BT and has to calculate the characteristics and capabilities of antennae and amplifiers, and although a large part of his job is writing bespoke programs to cope with the calculations, a calculator is still considered indispensable.
But it's really not my field of expertise, so I can't really shed more light than that. 




GuyBarry

1274834. Mon Feb 19, 2018 4:02 am 


Spud McLaren wrote:  I'm told that all sorts of scientific and engineering operations use base 10 logs, notably analogue electronics. 
Oh yes, some units are defined in terms of base10 logs, such as the decibel, which is 1/10 of the base10 log of the ratio of the power levels. pH values in chemistry are defined using base10 logs as well (negative of the base10 log of the activity of the hydrogen ion). Can't think of any others offhand but I'm sure there are a few more.
On the other hand, some units are defined using base2 logs, such as the cent (for measuring musical intervals), which is 1200 times the base2 log of the ratio of the frequencies. And you don't generally get a base2 log button.
(Not that it matters particularly, because you can calculate logs to any base with the changeofbase formula. And some modern calculators include a "log to any base" button.) 




GuyBarry

1274835. Mon Feb 19, 2018 4:13 am 


suze wrote: 
The good husband knows how to do hard arithmetic on a slide rule, but only because his grandfather gave him one when he was about eight. He doesn't think he ever used a slide rule at school, and I certainly didn't. 
Same here  I was given a slide rule to play with when I was a child in the 70s, although they were going out of fashion even then. I had a book called "Teach Yourself the Slide Rule" by the wonderfully named Burns Snodgrass, who founded the Unique Slide Rule company in the 1920s. The rules in the illustrations were slightly different from mine and I remember wishing that I had a loglog scale, which was used to calculate powers and roots.
You couldn't use them to add or subtract of course, which was something of a limitation. 




Jenny

1274902. Mon Feb 19, 2018 11:59 am 


I remember my first husband using a slide rule when he was at school, but bear in mind he left school in 1966 and this was definitely pre the availability of electronic calculators.
I think I was later learning decimals than you, suze, because we were still working in predecimal currency and so at primary school we did a great deal of arithmetic in fractions, as well as adding, multiplying and dividing in pounds, shillings and pence (and halfpennies!)
Now of course I see the virtue of doing that in terms of teaching us to work in base 20 and base 12 as well as base 2, but I don't think it occurred to any of us at the time. 




suze

1274912. Mon Feb 19, 2018 12:32 pm 


GuyBarry wrote:  I remember wishing that I had a loglog scale, which was used to calculate powers and roots. 
Husband's slide rule does have that feature!
It's the sort of thing that you don't just throw out, so it's still in his desk drawer. But until the topic came up on here, he's not sure that it had been taken out of the desk drawer for a fair number of years. By now, he'll usually open a spreadsheet if he needs to do hard arithmetic.
Jenny wrote:  I think I was later learning decimals than you, suze, because we were still working in predecimal currency and so at primary school we did a great deal of arithmetic in fractions, as well as adding, multiplying and dividing in pounds, shillings and pence (and halfpennies!) 
This seems likely. Decimalization of the Canadian dollar was completed in 1870, so by the time I went to school there was no one alive who had ever had to deal with Canadian pounds, shillings, and pence, or Newfoundland gold doubloons. (The Newfoundland $2 coin was 22 carat gold until as late as 1894, and these days there is plenty of collector interest in them. There was never a $1 dollar coin, because it was considered that gold coins as small as they would necessarily have to be would be too fiddly.)
Metrication in Canada was only a year or two ahead of Britain, but I was never taught inches, ounces, or Fahrenheits in school. So I suppose the education system just felt that decimals were more useful than fractions, and so taught them first. 




GuyBarry

1274930. Mon Feb 19, 2018 2:32 pm 


suze wrote:  GuyBarry wrote:  I remember wishing that I had a loglog scale, which was used to calculate powers and roots. 
Husband's slide rule does have that feature! 
A friend of my mother's had a loglog slide rule and I remember going round to his flat and being very impressed by it. (Incidentally did you know that the loglog scale was invented by Peter Mark Roget, of Thesaurus fame?)
I've discovered Ron Manley's Slide Rule Site, which (believe it or not) contains almost the entire text and original illustrations of Burns Snodgrass's book here. They don't write instruction manuals like that any more! 




suze

1274947. Mon Feb 19, 2018 4:57 pm 


For which we should all be profoundly grateful!
While I am no fan of the modern manual which is so often a bad machine translation from Japanese accompanied by minuscule illustrations, Mr Snodgrass's style is positively Dickensian.
Husband's slide rule is in fact a Unique Universal II Slide Rule made by Mr Snodgrass's firm, and from another website (yes, there are two slide rule fansites!) you can see what it looks like here. The log log scales are not labeled, but they are the top and bottom scales on the instrument.
The Unique Slide Rule Company was based at Norfolk Laboratories, Old London Road, Brighton 6, Sussex, telegraphic address Sliderules Brighton. Its works are no longer in existence, and a Coop store stands where the slide rule factory once did.
The particular model seems to date from the 50s, and husband reckons that this fits since his grandfather was at that time a draughtsman in the employ of the National Coal Board and might well have needed a slide rule. Millions of them were made, and so they are readily available second hand for little more than £10. 




GuyBarry

1275293. Fri Feb 23, 2018 8:33 am 


By a strange coincidence, I went to a presentation yesterday about a job for which a knowledge of the twelve times table is almost certainly a requirement. In fact, they teach the multiplication tables as part of the training.
Can you guess what it was? Hint: it's to do with a new leisure facility that's opening soon.
Answer: Casino croupier 




Baryonyx

1275301. Fri Feb 23, 2018 9:32 am 


Darts? 




GuyBarry

1275303. Fri Feb 23, 2018 9:43 am 


I've given the answer in white above. I don't think you need to multiply by 12 in darts  two and three I suppose, for doubles and trebles, but otherwise it's all addition and subtraction. In any case, don't players calculate their own scores in darts? I've never seen a job advertised as a dartscorer. 




suze

1275312. Fri Feb 23, 2018 11:29 am 


Probably not any more because tournament darts is scored by computer, but there certainly used to be such jobs. Pub darts still makes use of a blackboard to record the scores, and the convention  in our pub at least  is that scoring one game entitles you to play its winner.
Since I do not frequent the sort of establishment which is in fact offering the job to which you refer, I don't know whether the math there too is by now done by computers. 



