1. The problem statement, all variables and given/known data How long does it take for a sum of money to double if it is invested at 8% compounded semi-annually? 2. Relevant equations A = P(1+i)n A: Compounded amount P: Initial amount i: Interest rate n: Period 3. The attempt at a solution A = P(1+i)n (2x) = (x)[1+(0.08)]2n (2n because it's compounded semi annually) 2 = 1.082n (x cancels out) 2n = log1.082 n = (log1.082)/2 n = 4.5032 per half a year Although the answer given at the back of the package is 8.836a. And I'm assuming "a" stands for annual. So I'm not sure where I went wrong. Any help is much appreciated! Thanks in advance!