>>>>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?
>>>>
>>>>Thanks.
>>>
>>>I believe, it depends on the method of calculation and definition of "annual interest rate", that partucular party is using.
>>>If it is a credit card, and you are getting bill by ordinary mail, then usually description is printed there. Having description you may derive a formula.
>>
>>It's an interest rate on a boat - I don't have any more information here, so I wanted to see the most general term.
>
>Simple interest or compound interest?

The matter is never simple when there's a party with interest involved :).