c#: sum of two double numbers problem [duplicate]

Question

Possible Duplicate:
Why is floating point arithmetic in C# imprecise?

Hi. I've got following problem:

43.65+61.11=104.75999999999999

for decimal is correct:

(decimal)43.65+(decimal)61.11=104.76

Why result for double is wrong?

Answer 1

This question and its answers are a wealth of info on this - Difference between decimal, float and double in .NET?

To quote:

• For values which are "naturally exact decimals" it's good to use decimal. This is usually suitable for any concepts invented by humans: financial values are the most obvious example, but there are others too. Consider the score given to divers or ice skaters, for example.

• For values which are more artefacts of nature which can't really be measured exactly anyway, float/double are more appropriate. For example, scientific data would usually be represented in this form. Here, the original values won't be "decimally accurate" to start with, so it's not important for the expected results to maintain the "decimal accuracy". Floating binary point types are much faster to work with than decimals.

Answer 2

Short answer: floating point representation (such as "double") is inherently inaccurate. So is fixed point (such as "decimal"), but the inaccuracy in fixed-point representation is of a different kind. Here's one short explanation: http://effbot.org/pyfaq/why-are-floating-point-calculations-so-inaccurate.htm

You can google for "floating point inaccuracy" or so for more.