text: why in the business world. is 3% not truly 3%? in terms of a bank. why do they have to have such stupid fancy calculations. for example.. if someone had say 100,000 in an account for simplicities sake... and they give you 3% interest.. the way they calculate it out. they multiply it times 31 and then divide by 365 and then multiply the % rate and come up with some stupid number. i mean why does it have to be that hard. cant they simply take 3% off the amount .. what is the deal with this. please help me understand.. it actually the way they calculate it out. doesn’t even come close to simply math calculations. in your example, the quoted "3%" refers to interest earned for an entire year.  you cannot expect to earn 3% for only one month.  each month may be as short as 28 days, or as long as 31 days, so the amount of interest is different each month.  if you calculate the interest each month for a year and add the 12 amounts, you will find the total really is 3% for the entire year (except for possibly a few cents difference because of rounding - our monetary system does not recognize fractions of a cent).  "3%" really is 3% in business, but your understanding of simple mathematics needs a little more work.