Some day when my smart phone can't access a calculator. And someday when I have a tape measure that reads to 5 decimal places!

Neat trick though.

Before calculators we used sly drools at school and I am sure they could do this calculation but I couldn't work those things out back then, let alone remember if they could even do it today.

Edited By Hopper on 15/04/2022 10:01:56

Though if you use 1m as your unit on the tape measure then should not be too hard to split the 1mm divisions and get 2449.5mm which would equate to 2.4495units

But you would need a sharp pencil and also a pin for the other end of the string

Edited By JasonB on 15/04/2022 10:12:45

Who remembers how to find the square root of a number with a tape measure, piece of string and a pencil. ?

I most certainly have never known of that method.

But, there again, I have never seen a tape measure that would provide a value for the square root of six to that may significant figures ( 2.44948).🙂

I was taught at secondary school to use 4-figure logs to base 10 which I found quite fascinating. I was never taught to use anti-logs, so worked it out for myself, then asked the maths teacher who effectively said,if it works for you, do it.

Slide rules, of which I still have three, were the province of Technical College maths. All three have the A, B, C & D scales which make square roots dead easy, but only the 5" Helix A50S has the K scale for cubes & cube roots. Simple means, simple devices, relatively coarse in precision, yet sufficiently good enough for most, if not all, practical purposes. The only problems are the requirement to be able to work out the multiples of 10 required (sorry, forgotten the correct term here), and the difficulty in learning how to use them.

As far as square roots are concerned, there is a method, which I've now forgotten, whereby they could be calculated using the old, original 4 function plus K constant calculator. I seem to think that the method could be done longhand. Plus, I have a recollection that an expansion to the key sequencing could be used to produce cube roots.

Ah, happy memories.

Peter G. Shaw

In addition to using a tape measure, string and pencil to get square root 6, who can remember how to divide a line into any number of equal parts using just a straightedge and pencil?

Dave,

Try drawing a circle at the centre of the line

I was educated after slide rules and before calculators so it was all meant to be done the hard way. I was taught about log tables and used those, plus my brother being that much older was taught and had a slide rule. He didn't need it so it became mine and I found out it was not against the rules to use one. I was the only one to use a slide rule in my entire year.

I can still remember buying my first calculator at Uni, still have it too.

I have this in my watch list as a thing to do some day https://www.youtube.com/watch?v=HBdVVFqTrUU

Edited By AdrianR on 15/04/2022 11:41:49

SOD needs to move his circle 3.5 units to the right. It works because the vertical is then sqrt(3.5^2 – 2.5^2) from pythagorus. Using the difference of 2 squares, 3.5^2-2.5^2 =(3. 5+2.5)*(3.5-2.5),which is 6

I'm not sure how you can be "after slide rules". I went from log tables to slide rules to calculators, missed out on those mechanical things where you wound a handle till it went 'ping', but there was one in the first DO I worked in, and it was reputed that one of the old guys knew how to work it. To use the first electronic one you had to beg the chief engineer for a borrow, and sign for it. It was the size of a decent book.

There is an arithmetic method of finding a square root using something resembling long division, but having never used it in nearly 70 years, I can't remember how it works. If I need a square root these days (not very often) I use a calculator, although I still have a couple of slide rules and some log tables stuck in a drawer somewhere.

I have recently rediscovered my slide rule and started using it. If you only need an accuracy of three significant figures it is far quicker and less tiring on my artheritic fingers than a calculator.

As a student, or school kid, if you could not afford a slide rule there were always log tables. I remember a class at tech splitting in two and having a race between slide rules and log tables.

I remember being shown how to calculate a square root at school which was far more complex than using logs. Using square root tables was even easier.

JA

Thanks Duncan. Much closer, but still not right, 2.4236 instead of 2.4494

After a strong coffee I shall tackle Pythagoras!

Just in case anyone needs more accuracy the square root of 6 to 1000 places of decimals is:

2.449489742783178098197284074705891391965947480656670128432692567250
96037745731502653985943310464023481859460122661418912485886545983775
73416257839512372785528289127475276765712476301052709117702234813106
78986690853632443352545604033808808939374585567846574724361304144270
27021617420183830008158980783801308970072869399363083715809440080044
37386875491645146539391450120447264481333162935109447418135132854950
44466171726631425497648318124504011566045364590093435861679319836656
66266909131906535863766105258156179366236179110294672088354575512883
55298983241005586902050064154661241173533994104310579928984673395325
52787360418296551718303910367800383623166297323302829049773910474263
60070512637697546888677006409929559257173284645028880915144257463026
02952963237075525034227559915454262812980030646720799424253022878426
20534067947860046596939979935597540616713586546534562482082562768863
69280941306372433508864801572484633723244737954548814438479336370091
97410147785232875591063159846078310367009535324726

Put that in your slide rule and smoke it!

Dave

Either SOD has done it wrong, or QCad isn't as good as it thinks it is

Why is putting images in here such a faff!