Answer: Approximately 12.8 years.
Explanation:
Formula to calculate accumulated amount (compounded annually): [tex]A=P(1+r)^t[/tex] , where r= rate of interest , t= time
As per given, A= $68,000, P=$36,840 , r=4.9%= 0.049
To find : t
Substitute all values in formula , we get
[tex]68000=36840(1+0.049)^t\\\\\Rightarrow\ \dfrac{68000}{36840}=(1.0.049)^t\\\\\Rightarrow\ 1.84582=(1.0.049)^t[/tex]
Taking log on both sides , we get
[tex]\log(1.845819)=t\log(1.049)\\\\\Rightarrow\ t=\dfrac{\log(1.845819)}{\log(1.049)}\\\\\Rightarrow\ t=\dfrac{0.266189112}{0.020775488}=12.8126\approx12.8[/tex]
Hence, it it will take approximately 12.8 years.