Answer:
5.7% per year
Step-by-step explanation:
For an ordinary annuity, the final amount can be calculated by:
[tex]A = R*(\frac{(1+\frac{r}{n})^{nt}-1 }{\frac{r}{n} } )[/tex]
Where A is the final amount, R is the value invested monthly, r is the annual interest, n is the number of months in a year, and t the time in years. So:
[tex]155,514 = 675*(\frac{(1+\frac{r}{12} )^{156}-1}{\frac{r}{12} })[/tex]
(\frac{(1+\frac{r}{12} )^{156}-1}{\frac{r}{12} }) = 230.39
[tex](\frac{(1+\frac{r}{12} )^{156}-1}{r}) = 230.39/12[/tex]
(\frac{(1+\frac{r}{12} )^{156}-1}{r}) = 19.2
Solving that in a graphic calculator,
r = 0.057
r = 5.7% per year
