If the compound interest for the 3rd and 4th year on a certain principal is Rs. 125 and Rs. 135 respectively, what is the rate of interest (in %)?

8%

Compound interest for the 3rd year = 125

Compound interest for the 4th year = 135

R% = \(\frac{ (CI \; for \; 4 \; years) - (CI \; for \; 3 years) }{(CI \; for \; 3year)}\)

R% = \(\frac{135 - 125}{125}\) × 100 = 8%