The true discount on a bill for Rs. 2520 due 6 months hence at 10% per annum is

$$\eqalign{ & F = {\text{Rs}}{\text{.}}\,2520 \cr & T = 6\,{\text{months}} = \frac{1}{2}\,{\text{years}} \cr & R = 10\% \cr & TD = \frac{{FTR}}{{100 + \left( {TR} \right)}} \cr & \,\,\,\,\,\,\,\,\,\,\,\, = \frac{{2520 \times \frac{1}{2} \times 10}}{{100 + \left( {\frac{1}{2} \times 10} \right)}} \cr & \,\,\,\,\,\,\,\,\,\,\,\, = \frac{{1260 \times 10}}{{100 + 5}} \cr & \,\,\,\,\,\,\,\,\,\,\,\, = \frac{{12600}}{{105}} \cr & \,\,\,\,\,\,\,\,\,\,\,\, = \frac{{2520}}{{21}} \cr & \,\,\,\,\,\,\,\,\,\,\,\, = {\text{Rs}}{\text{.}}\,120 \cr} $$