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

For 1st year
Principal (P) =Rs. 15000, Rate (R) =6%
Time(T) =1 year
$\therefore$ Interest = $\frac{15000\times 6\times 1}{100}=150\times 6$ =Rs. 900
$\therefore$ Amount at the end of 1st year
=Rs. 15000+ Rs. 900=Rs. 15900
For 2nd 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 2nd year
=Rs. (15900+1272)=Rs. 17172
For 3rd 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 3rd year
=Rs. (17172+1717.20)=Rs. 18889.20
$\therefore$ Compound interest= 18889.20-15000
=Rs. 3889.20