If the compound interest for the 2nd and 3rd year on a certain principal is Rs.55 and Rs.60 respectively, what is the rate of interest (in %)?

9\(\frac{1}{11}\)%

Compound interest for the 2nd year = 55

Compound interest for the 3rd year = 60

R% = \(\frac{ (CI \; for \; 3rd \; year) - (CI \; for \; 2nd\; year) }{(CI \; for \; 3rd \; year)}\)

R% = \(\frac{60 - 55}{55}\) × 100 = 9\(\frac{1}{11}\)%