how long would it take money to triple in an account with a one-time deposit earning 9% interest compounded two times per year?
1(1.045)^n = 3, where n is the number of half-years.
using logs ...
n log 1.045 = log 3
n = log3/log1.045 = 24.95888
or 25 half-years.
I would say 12.5 years.