The present worth of a certain bill due sometime hence is Rs. 800 and the true discount is Rs. 36. The banker's discount is:

$$\eqalign{ & B.G. = \frac{{{{\left( {T.D.} \right)}^2}}}{{P.W.}} \cr & = Rs.\,\left( {\frac{{36 \times 36}}{{800}}} \right) \cr & = Rs.\,1.62 \cr & \therefore B.D. = \left( {T.D. + B.G.} \right) \cr & = Rs.\,\left( {36 + 1.62} \right) \cr & = Rs.\,37.62 \cr} $$