Converting fractions to decimals

Yep Duncan, I remember using the hurdy gurdy for doing circlip design calcs and as far as logs were concerned, plenty of class 365s and 465s DMUs hurtlling about with stainless exzorsts.

Regards Ian.

I'm not suggesting using logs gives the wrong answer, but it takes longer for no benefit, and as it takes longer it costs more

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I presume that you write in jest, Duncan … But just in case: The point was that the fractional calculation is exact, and the decimalisation thereof is only done on the answer.

MichaelG.

Look at the top left of the screen on Michael's first image it has the metric answer to 3 decimal places not just the 80ths

Steady guys - that (and the other replies) seems a long way to get to the answer

1 1 / 1 6 + 1 x 2 5 . 4 = (thirteen inputs on a conventional basic calculator) amazingly gives the same answer - 42.8625

Ah but of course I know you want to show all that mathematical prowess you all possess to an old numbskull like me. Impressive of course but neccessary - hmmm not so sure on that - I'll bow out here me thinks.

Great topic and good comments though

Tug

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Sorry if it wasn’t self-evident, Tug

The working that I showed is the way the Calculator does it … That listing is available at the touch of the button at top right of the display.

Please see my post at 08:51:28 this morning.

MichaelG.

Edited By Michael Gilligan on 17/08/2021 17:03:31

And Less input from you too Michael as there is no need for the / and + in Tugs example so just 11 buttons to press

Edited By JasonB on 17/08/2021 17:06:07

Oh no, one of us must be wrong! Surely not me?

Sadly it's true, I've cocked up AGAIN!

Sorry,

Dave

PS Nurse says bed with no supper tonight...

There's much shorter approach by calculator than that shown; as Tug describes and I would do it:

1) Divide 11 by 16.

2) Add 1.

3) Multiply by 25.4.

= 42.8625

OR....

1) Divide 27 by 16. (27 = 16 + 11; simple enough for mental arithmetic more rapid than Steps 1) and 2) above.

2) Multiply by 25.4.

= 42.8625

On some calculators you may need use the equals sign at the appropriate point in either method.

A waltz and a two-step! Not sure what the photographed umpteen-step example is on that theme... More like Strictly Come Dancing.

Ah I see now Michael

Ok you (all) have me convinced - well, sort of - but I still don't see the need to go there myself so I'll keep tapping those keys if only to give my fingers some exercise - what was it 'they' say about old soldiers - fading starts here I guess

I've a few years left as yet I hope but I guess I won't see too much spot changing in my future

All the best guys - Tug

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It is, as already stated, the Fractional Calculator’s own explanation of its work.

The example quoted was trivial. … the App is [again, as already stated] capable of much longer calculations with fractions.

… I’m beginning to wish I hadn’t mentioned it.

MichaelG.

Well - there you go part two! Thanks Nigel.

Something else learnt - had never seen or thought to do that before believe it or not but makes total sense.

So now own to Jason,s/Michael's 11 inputs but, if the 25.4 is in the memory it comes down to 9 - it gets less onerous per post!

See, a (basic) calculator is all you need after all

Apologies Michael

Tug

Edited By Ramon Wilson on 17/08/2021 17:58:16

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No apology needed !!

The opening line of my first post in this thread was :

I’m not taking sides… each to his own

MichaelG.

Kind of brings up back full circle to the chart or a spread sheet. Dozen clicks to start with and then no more. How many times would you have to enter those 9 digits on a drawing like your triple? 100 maybe or more so that's 900 presses vs 12. Sheet or part sheet of paper on the desk infront of you takes up no more room than a calculator. And with that chart from the first post there is no need to add on the full inch dimensions or add multiples of the divisor be it in your head or with a calculator. Click image to get it larger.

Edited By JasonB on 17/08/2021 18:38:20

Hi MichaelG, every day is a school day, so no need to regret mentioning it, if nothing else I've learnt a couple of different ways to use my calculator and it's been interesting to see the full fractional calculation of a simple sum. My late elder brother was really very good at maths and I can still remember him working out quite long and sometimes complex equations in his head while using a slide rule, my siblings and myself would turn to him for help if we were struggling with our maths.

Regards Nick.

Edited By Nicholas Farr on 17/08/2021 18:49:43

Thanks for that Tim. Some good charts.

Steve.

Perhaps we could have a fractional micrometer?

The slide rule has yet to be put away but I am redrawing the model (to metric) using my own spread sheet.

JA

but 40.8625 is exact, because 1/80 = 0.0125 exactly, so multiples are exact at 4 decimal places (or 3 for even numbers off). I was just making the point that 42 + 69/80 is a fairly useless dimension. Actually converting any number of 1/128" to metric gives a decimal number within the precision of my calculator, 25.4/128 = 0.1984375 exactly. In reality I'd use 0.20 as my DRO doesn't do better than 0.005

Yes there will be some situations where the decimal runs out of decimal points, but not model engineers converting imperial fraction lengths to metric.

Edited By duncan webster on 17/08/2021 22:16:08

I was responding more to the comments on using calculators in response to Tims first post but I concede Jason (and Tim), that is a good chart.

One would still have to ammend the drawing annotation however (or refer to the chart each time) and use a calc to add accumulated dimensions - personally, I certainly couldn't keep something like that in my head so, as with so many things - it's down to choice - my initial comment was that I didn't see why using a calc was percieved as an issue. I'm afraid I still don't but certainly agree, that the chart that Tim suggests would be a useful addition to the workshop

I have a very nice small, hand held plastic coated chart - similar lay out to the Zeus chart but personally I find it quicker ? easier? to just punch what I want into the calc. Habit I guess.

Just the way I have developed working over these years - paying money and taking a pick springs to mind

Nothing about sides Michael just your line - … I’m beginning to wish I hadn’t mentioned it.

Apologies were for the further perpetuation

Tug

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That was more a reaction to Nigel’s dig at me

… Water under the bridge

MichaelG.