How to keep decimal precision when multiplying and dividing (in jQuery, javascript)?

Question

I have the following function that can do multiplication and division for some business logic in jQuery

var rate = 39.5;
var IndiviualPercentageTaxes = 20;
var TotalPercentageTaxes = 20;

var r1 = rate* 100 / (100 + IndiviualPercentageTaxes);  

var r2 = r1* (100 + TotalPercentageTaxes)/100;

var finalRate = Math.round(r2));

FinalRate 39 , but the expected result is 40 .....

I can easily rewrite the program to avoid losing decimal precision in the calculation, for example:

  var r2 = rate*(100 + TotalPercentageTaxes)/(100 +TotalPercentageTaxes)

However, this will skip r1, and I need r1 for other purposes throughout the program.

It also caused confusion that no one knows what this formula means, since I combine two calculations in one.

Are there any suggestions?

Answer 1

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