The banker's discount and the true discount on a sum of money due 8 months hence are Rs. 120 and Rs. 110 respectively. Find the rate percent.

Answer: Option D

$$\begin{array}{rl}& \text{Sum}=\frac{B.D.\times T.D.}{B.D.-T.D.}\\ & =\text{Rs}\text{.}\frac{120\times 110}{120-110}\\ & =\text{Rs}\text{.}1320\end{array}$$
Since B.D. is S.I. on sum due, so S.I. on Rs. 1320 for 8 months is Rs. 120.
$$\begin{array}{rl}& \text{Rate}=\frac{100\times 120}{1320\times \frac{2}{3}}\%\\ & =\frac{150}{11}\%\end{array}$$