If a sum of money amounts to Rs.2750 in 3 years and Rs. 3375 in 5.5 years at the same rate of simple interest per annum.The rate of interest is:

12.5%

S.I. in 2.5 years = S.I. in 5.5 years - S.I. in 3 years

                         = ₨.3375 - ₨.2750

                        = ₨. 625

S.I. in 1 year = \(\frac{625}{2.5}\)

                     = ₨.250

Principal = ₨.2750 - (₨.250) x 3

             = ₨.2750 - 750

             = ₨.2000

rate of interest = \(\frac{250}{2000}\) x 100

                      = 12.5 %