Question

calculate compound interest

Answer 1

A ⇒ P × $( 1 + \frac{r}{n} ) ^{nt}$

Where A = Amount Accumulated ,
P = Principle ,
r = rate of interest ,
n = compounding per period ,
t = no. of periods. 

Answer 2

If you want to calculate compound interest(CI) for Principal=P, at the rate =R %, for a time period = t, compounded n times a year(compounded annually means n=1);
The total amount(A) will be

$A=P(1+ \frac{r}{100n})^{nt}$

$CI= A-P=P(1+ \frac{r}{100n})^{nt} - P=P[(1+ \frac{r}{100n})^{nt}-1]$