Compound Interest Compounded Half-Yearly

When interest is compounded half-yearly (twice a year), the annual rate $r\%$ is halved to get the rate per half-year, and the number of compounding periods is doubled, since there are 2 half-years in every year. For a principal $P$, annual rate $r\%$, and time $t$ years, the amount is

$A = P\left(1 + \frac{r}{200}\right)^{2t}$ …