Answer: Rate of return = 25%
Sum invested \( = 50 \times 80 = ₹\,4000 \)
Dividend is on face value: per share \( = 20\% \text{ of } 100 = ₹\,20 \); total \( = 50 \times 20 = ₹\,1000 \).
\[ \text{Rate of return} = \frac{1000}{4000} \times 100 = 25\% \]