Answer: 9 years
Step-by-step explanation:
Let 's use the compound interest formula :
[tex]\rm \displaystyle S=A\left( 1+\frac{N}{100} \right)^{\rm \big r}[/tex]
Where N- the percentage by which we raise the price ; r-years ; A-the original price
In our case
N=3,5% ; r=? ; A=590$
And we know :
[tex]\rm \displaystyle S= 800 \\\\ 590 \left( 1+ \frac{3,5}{100} \right)^{\big {r}}=800 \\\\\\(1,035)^{\big r} = \frac{80}{59}\approx1,355 \\\\\\ r= \log_{1,035}\ 1,355=8,\underline831 \approx9 \ years[/tex]
