The banker’s discount on a sum of money for 1(1/2) years is Tk. 558 and the true discount on the same sum for 2 years is Tk 600. The rate percent is -

Banker's Discount for 3/2 years = Tk. 558
Banker's Discount for 2 years = Tk. {558 × (2/3) × 2}
= Tk. 744
True Discount for 2 years = Tk. 600
∴ Sum = {(B.D × T.D)/(B.D - T.D)}
= Tk. {(744 × 600)/(744 - 600)
= Tk. (744 × 600)/144
= TK. 3100
Thus, Tk. 744 is Simple Interest on Tk. 3100 for 2 years
∴ Rate = {(100 × 744)/(3100 × 2)}%
= 12%