current worth = 10,000,000 * (1.03)^years
We must determine the years when current worth = 13,000,000
13,000,000 / 10,000,000 = 1.03^years
1.3 = 1.03^years
Taking logs of both sides:
log (1.3) = years*log(1.03)
log(1.3) / log(1.03) = years
0.11394335231 / 0.012837224705 = years
years = 8.8760113598
Roughly about 8.9 years