The banker's gain on a certain sum due 2 1/ 2 years hence is (3/23) of the banker's discount. The rate per cent is?

Let B.D. be Re. 1. Then B.G. = Re. (3/23)
∴ T.D.= Re. (1 - 3/23) = Re. (20/23)
Sum = Rs. [(1 x 20/23 / (1 - 20/23)] = Rs. 20/3
∴ S.I. on Rs. 20/3 for 2¹/₂ years is Re. 1
∴ Rate = (100 x 1 / 20/3 x 5/2)% = 6%