On 07/03/2018 11:44, clipka wrote:
> Sorry to be blunt, but with that many decimals, that number is a lie, as
> it implies a precision it doesn't have.
> 

You are right of course, if bluntly put.

> As a rule of thumb, whenever you're doing mathematical computations with
> approximate values, it is good practice to round the end result to the
> lowest number of significant digits of any of the "input" values.
> 
> Also, since the UK imperial and US customary units are defined in terms
> of the metric system (yes, you UK folks have been using the metric
> system ever since 1930, and you US folks even since 1893(*); it's just
> been hidden from you :P), that's what I'd recommend to start with:

Now, I would be surprised if people in the UK did not know that. I guess 
I was about 15 or 16 when I was taught it at school.
But as a rule of thumb that an inch is about the length of your thumb's 
distal phalanx. Is good enough for children as they more resemble the 
size of an adult of bygone years.

BTW has anyone heard or seen a ruler where feet are divided into tenths?
Giving the impression that there are 10 "X inches" to a foot.
I saw one once about 30 years ago.


-- 

Regards
     Stephen

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