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In a book named " Concepts of Physics" by H.C Verma , it was said that " when there is 5 after the decimal point and the number immediately before the decimal point is an even number it doesn't change . Example - Rounding off 2.5 to nearest ones is 2"

But from my high school days I have been learning that 2.5 rounded off to nearest ones is 3 .

I am really confused what to follow ?

World Producer
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  • In scientific computing you will usually use a working precision (e.g., 15.5 decimal digits) that is several digits longer than the display or export precision (e.g. 10 digits). Then it is highly unlikely to get $x.5000$ as result, so that this singular case barely matters. // In money matters the round-to-even rule may give a neutral average of zero for the rounding amounts, while the rounding-up-rule could be slightly biased. – Lutz Lehmann Apr 17 '23 at 12:11

1 Answers1

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I was taught the same in High-School as well.

The rule went like this:-

A number in decimals, let's say "x.y" needs to rounded off,
then   
check whether y > 5, if yes, x.y = x+1  
check whether y < 5, if yes, x.y = x  
if y = 5, then check if x is even or odd,   
if even, x.y = x else x.y = x+1.

In life out of school, we follow the rules that best suit our purpose.

For example, rounding off numbers like above method might have made sense in a physics class involving measuring instruments, (like learning to use vernier calipers). These numbers are nothing but data.

In real life, data is used to represent a certain statistic that conveys some information. Rounding off a quantity, means to "compress" this data into more comprehensible units. Either you can say the elapsed time was 2.441s or 3 seconds. Or the shuttle missed its mark by 1.145cm or 1 centimeter.

In rounding off data, you decide between losing some data or gaining some garbage data; and which of them would be lesser of a problem.

One more example, sometimes we can "sample" some data for another system which could result in loss of some data (Analog to Digital Conversion).

Kartik Pandey
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  • @ronno As in engineering, I would have rounded off according to the method I mentioned. I guess, accountants stick to an even number (can't say for sure). OP needs to mention where did he round off 2.5 to 3. – Kartik Pandey Apr 17 '23 at 14:04
  • I mean, what is the relevance of most of the answer, starting with "For example..."? The question is about picking one method over another and what you say applies to both methods equally. – ronno Apr 17 '23 at 14:08
  • OP is clearly a student. Having read similar textbooks like HC Verma myself. This question of OP is more of naivety rather than a genuine one between choosing a method. Such estimation methods are subject to convention more than anything. But I believe passing hot-takes is against stack-exchange rules. (new here). – Kartik Pandey Apr 17 '23 at 15:02
  • Context matters. I had a chat with my brother, he is an accountant. He said he will definitely round off to the next integer, if ever needed. (He can not show losses on sheets, boss will fire him).

    Engineers (or researchers) can back or forth, our objective is to be as close to accuracy as possible. Data point would possibly be in metric spaces.

     – Kartik Pandey Apr 17 '23 at 15:06
  • I just don't see how this is answering the question. If you think there's a different (better) question to be answered feel free to ask and self-answer it. If your answer was along the lines of "there is no real difference, it's just a matter of convention" then it would at least answer the question (although I would still disagree). I don't think it matters if the take is "hot" if you explain and justify it. – ronno Apr 17 '23 at 15:08