To solve this type of question, we can use the formula for simple interest:
[tex]A=P(1+rt),[/tex]where A is the final amount, P is the initial amount, r is the annual interest rate, and t is the time in years.
Substituting A= 1000, t=4, and r=0.05, we get:
[tex]1000=P(1+0.05\times4).[/tex]Solving the above equation for P we get:
[tex]\begin{gathered} \frac{1000}{(1+0.2)}=P, \\ P=\frac{1000}{1.2}, \\ P=833.3\bar{3}. \end{gathered}[/tex]Answer: He invested
[tex]833.\bar{3}.[/tex]