Investor purchased 50 shares of stock in a company for $40.
So, the total initial amount he invested is
[tex]50\cdot40=2000[/tex]Then the rate of return is:
[tex]\begin{gathered} \text{rate of return=}\frac{shares\text{ sold price-initial amount invested}}{\text{ initial amount invested}}\cdot100 \\ =\frac{2200-2000}{2000}\cdot100 \\ =\frac{200}{2000}\cdot100 \\ =10 \end{gathered}[/tex]So, the requied rate of return is 10.0%.