Annual Interest Rates

Question

 For how many months do you need to invest your money into a bank account earning an annual interest rate of 11.59% compounded monthly if you want to triple your investment?

Answer 1

A = P(1+r/n)^nt

where

A=ending Amount

P=starting Principle

A/P =3 for tripling the investment

r=annual interest rate= 11.59% = 0.1159

n=number of compounding periods per year= 12 for monthly compounding

t = years

A/P = 3 = (1+.1159/12)^12t

solve for t

12t=about 114.3

t =114.3/12

= about 9.525 years to triple the investment

= about 114.3 months to triple the investment