Question

The simple interest on a certain sum at $5$ per annum for $3$ years and $4$ years differ by Rs. $42$. Find the sum?

Answer 1

Simple Interest$=\frac{PTR}{100}$

Simple Interest for $3$ years$=\frac{P\times 3\times 5}{100}$

Simple Interest for $4$ years$=\frac{P\times 4\times 5}{100}$

Given:Simple Interest for $4$years$-$Simple Interest for $3=$Rs.$42$

$\Rightarrow \frac{P\times 4\times 5}{100}-\frac{P\times 3\times 5}{100}=42$

$\Rightarrow \frac{20P}{100}-\frac{15P}{100}=42$

$\Rightarrow 5P=4200$ or $P=\frac{4200}{5}=$Rs.$840$

$\therefore$ sum$=$Rs.$840$