A sum of Rs. 2600 is invested at two different rates of interest. The difference between the simple interests got after 4 years is Rs 402.80 at these two rates, what is the difference between the rates of interest?

Let the two different rates of interests be r1 and r2 respectively.

From the given data,

$\frac{2600 x 4 x r1 - r2}{100 } = 402.80r1 - r2 = \frac{402.80}{104} \; =\; 3.87$

Hence, the difference in the interest rates = 3.87