A person invested $3,600 in an account growing at a rate allowing the money to
double every 13 years. How long, to the nearest tenth of a year would it take for the
value of the account to reach $11, 300?
I got 13 years for a single (7,200), then I got the amount rounded to the nearest tenth and got the amount of years out of 13. Then, I added that into 13 to get 20.8!