Interest in Your Bank Account
July 20, 2010 1 Comment
Suppose you have £100 and you wish to put it into a savings account for a year, and the interest rate is 5% per annum. What does this mean?
Well, it could mean a few things.
First, it could be that the interest rate is applied at the end of the year. So at the end of the year you get:
However, it could also mean that there is a 2.5% interest rate applied twice in a year:
Earning you a little bit more! Suppose instead that the interest was applied every day:
In general, if it is updated h times in a year, with an annual interest rate p, then it is equivalent to the interest being calculated once at a rate of:
So what if it was updated all the time? It is well known that the above expression tends to as .
The point is just that these things can come up naturally! This is actually widely used when trading derivatives.
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