The banker's discount on a sum of money for 1 1/ 2 years is Rs. 60 and the true discount on the same sum for 2 years is Rs. 75. The rate per cent is?

B.D. for (3/2) years = Rs. 60
B.D. for 2 years = Rs. (60 x 2/3 x 2) = Rs. 80
Now, B.D. = Rs. 80; T.D. = Rs. 75
and Time = 2 years
∴ Sum = Rs. (80 x 75 / 5) = Rs. 1200
∴ Rs. 80 is S.I. on Rs. 1200 for 2 years.
So, rate = (100 x 80/1200 x 2)% = 3¹/₃%B.D. for (3 / 2) years = Rs. 60
B.D. for 2 years = Rs. (60 x 2 / 3 x 2) = Rs. 80
Now, B.D. = Rs. 80; T.D. = Rs. 75 and Time = 2 years
∴ Sum = Rs. (80 x 75 / 5) = Rs. 1200
∴ Rs. 80 is S.I. on Rs. 1200 for 2 years.
So, rate = (100 x 80 / 1200 x 2)% = 3¹/₃%