The difference between the simple interest received from two different sources on Rs. 1500 for 3 years is Rs. 13.50. The difference between their rates of interest is ?

Answer: Option C

Let the rate of interest for two different sources is r₁ and r₂ respectively.
$$\begin{array}{rl}& \frac{1500\times {\text{r}}_1\times 3}{100}-\frac{1500\times {\text{r}}_2\times 3}{100}\\ & =13.50\\ & 4500{\text{r}}_1-4500{\text{r}}_2=1350\\ & \left({\text{r}}_1-{\text{r}}_2\right)=\frac{1350}{4500}=0.3\%\end{array}$$
Hence required difference in rates = 0.3%