Question

At what rate percent of simple interest will the interest on $Rs.3,750$ be one-fifth of itself in $4$ years? To what will it amount in $15$ years?

Answer 1

$SI=\frac{P}{5},t=4$

$SI=\frac{Prt}{100}$

$\frac{P}{5}=\frac{4Pr}{100}$

$⟹r=5\%$

Now, when $t=15$

$SI=\frac{3750\times 5\times 15}{100}=Rs.2812.5=\frac{3}{4}\left(3750\right)$

$⟹SI=\frac{3}{4}P$