Say someone got a loan for $30,000. They promised to pay back $1,000 a month for 3 years. At the end of the 3 years they would have paid back $36,000. How do you calculate the interest rate on the loan?

Calculate this for me. Invest $1000. for a 3 month term and the interest rate is 8.50%. What is the interest that will accured for the 3 month term? Best logical answer please. Thanks.

I understand that banks, for deposit a/c, although they advertise an annual interest rate, they actually calculate a daily rate and take the year as 360 days! Is that correct? So as an example, If I deposit $1000 at 5% pa, how much will they pay me per month?. All months do not have the same number of days and whatever they say at school, there are unfortunately, many ways of calculating compound interest. Could some one with practical experience please show me the calculation banks do?

PV being present value, FV future value and time. Also, how would one figure out the amount of time it takes for an amount to reach a certain amount...let's say $400 to 1,000 at an interest rate of 4?