Loan Calculator Java

Question

https://www.sololearn.com/learning/eom-project/1068/949

My first answer to the task was this:

for(int i = 1; i <= 3; i++){
amount /= 100;
amount *= 90;
}
System.out.println(amount);

It does work for the first 2 test cases, but not for the remaining 3.
When I rewrite the code to this

amount = amount * 90 / 100;
or
amount *= 90;
amount /= 100;

it's working for all 5 test cases.
I can't really retrace what the difference between the two calculations is, since only the first two test cases are open (Test Case 1 Input: 100000, Output: 72900; Test Case 2 Input: 500000, Output: 364500). Explanations and especially examples are higly appreciated!