Question

A sum of money amount to $Rs.780$ in two years and $Rs.1230$ in seven years. Find the principal and rate of simple interest.

Answer 1

$2$ years $\to 780$

$5$ years $\to 450$

$7$ years $\to 1230$

$5$ years $\to 450$

$1$ year $\to ?$

$?=\frac{450\times 1}{5}=90$

$2$ years$=90\times 2=180$

Principal$=780-180=600$

$R\%=\frac{100\times 90}{600}=15\%$.