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On a certain screen I take a value and add 10% on top of that value.
100,00 + 10% = 110,00
I save the final amount (110.00). I’m having difficulty in picking up the final amount (110.00) and taking the 10%. 110.00 - 10% = 99.00 and in real I wanted to return to 100.00.
I found the following formula in java, but it is going wrong in some cases, as 220,00
Double ofertaNormal = proposta.getOferta() / (1+(10.0/100));
ofertaNormal = (double) Math.round(ofertaNormal);
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10% of 110 is 11, so the result is correct. To get 100, the question is "what is 110 when you add 10%?":
1.1x = 110
Soon:
x = 110 / 1.1
x = 100
Edit: Your Java code looks right. If you are having problems with broken numbers, it is because of an inherent accuracy problem with Double (see here an explanation; the question is about Javascript, but the problem is the same in Java with Double and Float). In this case I believe you can use BigDecimal instead of Double.
The 220.00 is correct, but with broken numbers, for example 4.02 it is going wrong
Thank you very much, I’ll take a look
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my... 10% of 110 is 11 and not 10...
– Gabriel Gartz