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 ?

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