>Hi everybody,
>
>If I have an item which cost $100 and the annual interest rate is 2% and the days of interest 10, how can I calculate the actual interest cost?
>
>Can you give me the exact formula, please?

Interest=principal*(rate*days/36500)

You can go at this step by step - calculate the annual interest (principal*rate/100) then multiply that with the proportionate part of the year (days/365) but the result should be the same, save for roundoff errors happening in a different order.