Simple interest of $₹\ 400$ for one year is $₹\ 40$. What is the interest $₹\ 600$ for $5$ years if the rate of interest remains same?

Given: Simple interest of $₹\ 400$ for one year is $₹\ 40$.

To do: To find the interest $₹\ 600$ for $5$ years if the rate of interest remains same.

Solution:

As given Principal amount $P=₹\ 400$

Time $T=1\ year$

Simple interest $I=₹\ 40$ 

$R=?$

Therefore, simple  $A=\frac{PRT}{100}$

$\Rightarrow 40=\frac{400\times R\times1}{100}$

$\Rightarrow 40=4R$

$\Rightarrow R=\frac{40}{4}$

$\Rightarrow R=10$ %

Now for Principal Amount $P=₹\ 600$

Time $T=5\ years$, Rate$=10$ %

Therefore, simple interest on $₹\ 600$ for $5$ years $A=\frac{PRT}{100}$

$=\frac{600\times10\times5}{100}$

$=₹\ 300$