20. If $250 is invested in an account with interest compounded annually, and two years later, there is $273.53 in the accoundt, what was the annual interest rate for the account?
Standard formula: $\displaystyle S = P(1 + i)^n$
where S is the amount at the end of the time period, P is the initial amount (principle), i = (rate per annum)/(number of periods per year), n = (number of periods per year) (length of investment period).
In your problem, S = 273.53, P = 250, i = (rate per annum)/(1) = rate per annum, n = (1)(2) = 2.
Sub and solve for i.