vb.net - WRONG SUM OF DOUBLES IN VB .NET -

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hello i´m using microsoft vb 2012 , have problem sum of doubles.

this simple code reproduces it:

dim result double = 0 dim amount1 double = 81.83 dim amount2 double = 50.0 result += amount1 result += amount2 

result equal 131.82999999998 instead of 131.83

in fact:

dim test1 double = 81.83 + 50.0   '(= 131.82999999998 wrong) dim test2 double = 81.83 + 50     '(= 131.82999999998 wrong) dim test3 double = 81.83 + 10     '(=  91.83 ok) dim test4 double = 81.82 + 50.0   '(=  131.82 ok) 

can explain it?

best regards david

a double value can represent numbers exactly. values can approximated. see wikipedia more detailed explanation. have fixed number of decimal digits, depending on size of floating point number (compare single , double) , exponent represents number. due simple calculations may produce rounding errors.

to avoid can use datatype decimal represented , used financial calculation example avoid these errors.