How to fix the digits for the summation?

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MAHMOUD ALZIOUD 2019-4-10

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评论： Star Strider 2019-4-10

Dear All, I have a code that finds the percentage of each case from the total population, I have 10 cases and the summation of their percentages must be 100% or 0 for example, but the problem is that I am still getting a summation of 100.01 or 99.99 or 99.98, what is the reason here and how can I fix it please, Notice: I rounded the results into 2 digits before I calculate the summation.

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Adam 2019-4-10

It is not possible to store every floating point number precisely so there are errors that accumulate when they are summed (or other operations) which is why you will not get exactly 100 as your answer.

Read up about floating point arithmetic to understand further.

MAHMOUD ALZIOUD 2019-4-10

Thank you for your help, I will try it now

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Star Strider 2019-4-10

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See the documentation section on Floating-Point Numbers (link). You are most likely seeing the result of floating-point approximation error. Also, rounding the numbers first loses precision, and likely results in the inaccuracies you get. The solution is not to round the intermediate values, only the results, and the only if necessary.