Question

Calculate the compound interest on $Rs.15000$ in $3$ years; if the rates of interest for successive years be $6\%$, $8\%$ and $10\%$ respectively.

Answer 1

For $1$st year

Principal $\left(P\right)=Rs.15000,$ Rate $\left(R\right)=6\%$

Time $\left(T\right)=1$ year

$\therefore$ Interest $=\frac{P\times R\times T}{100}=\frac{15000\times 6\times 1}{100}=150\times 6=Rs.900$

$\therefore$ Amount at the end of $1$st year

$=Rs.15000+Rs.900=Rs.15900$

For $2$nd year

$P=Rs.15900,R=8\%,T=1$ year

$\therefore$ Interest $=\frac{15900\times 8\times 1}{100}=159\times 8=Rs.1272$

$\therefore$ Amount at the end of $2$nd year

$=Rs.(15900+1272)=Rs.17172$ [$\because$ Amount $=P+I$]

For $3$rd year

$P=Rs.17172,R=10\%,T=1$ year

$\therefore$ Interest $=\frac{17172\times 10\times 1}{100}=Rs.1717.20$

$\therefore$ Amount at the end of $3$rd year

$=Rs.(17172+1717.20)=Rs.18889.20$

$\therefore$ Compound interest $=18889.20-15000$
$=Rs.3889.20$