A certain amount money at R% compounded annually after two and three years becomes Rs. 1440 and Rs. 1728 respectively, R% is ?

Here, b – a = 3 – 2 = 1
B = Rs. 1728, A = Rs.1440
$$\eqalign{ & R\% = \left( {\frac{B}{A} - 1 \times 100} \right)\% \cr & \,\,\,\,\,\,\,\,\,\,\,\, = \left( {\frac{{1728}}{{1440}} - 1 \times 100} \right)\% \cr & \,\,\,\,\,\,\,\,\,\,\,\, = \left( {\frac{{288}}{{1440}} \times 100} \right)\% \cr & \,\,\,\,\,\,\,\,\,\,\,\, = 20\% \cr} $$