What would be the compound interest accrued on an amount of Rs. 8400 @ 12.5 p.c.p.a at the end of 3 years ?

Explanation:-

$$\eqalign{ & {\text{Amount}} \cr & {\text{ = Rs}}{\text{.}}\left[ {8400 \times {{\left( {1 + \frac{{25}}{{2 \times 100}}} \right)}^3}} \right] \cr & = {\text{Rs}}{\text{.}}\left( {8400 \times \frac{9}{8} \times \frac{9}{8} \times \frac{9}{8}} \right) \cr & = {\text{Rs}}{\text{.}}\left( {\frac{{382725}}{{32}}} \right) \cr & = {\text{Rs}}.11960.156 \approx {\text{Rs}}.11960.16 \cr & {\text{C}}{\text{.I}}{\text{.}} = {\text{Rs}}{\text{.}}\left( {11960.16 - 8400} \right) \cr & = {\text{Rs}}{\text{.}}\,3560.16 \cr}$$