For this case, what we should do is use the given equation. A = P (1 + r) ^ t Substituting values we have: 3900 = 1100 * (1 + 0.04) ^ t Clearing t we have: (1.04) ^ t = (3900) / (1100) log1.04 ((1.04) ^ t) = log1.04 ((3900) / (1100)) t = log1.04 ((3900) / (1100)) t = 32.3 years Answer: the time will be: t = 32.3 years