Principal sum = Rs. 4000 and time period = 1 year Let rate of interest = $$r\%$$
=> Amount after compound interest = Rs. 6000
=> $$P(1+frac{R}{100})^T=6000$$ => $$4000(1+frac{r}{100})^1=6000$$ => $$1+frac{r}{100}=frac{6000}{4000}=1.5$$ => $$frac{r}{100}=1.5-1=0.5$$ => $$r=0.5 imes100=50\%$$ $$ herefore$$ Amount after 4 years = $$4000(1+frac{50}{100})^4$$ = $$4000(1+frac{1}{2})^4=4000(frac{3}{2})^4$$ = $$4000 imesfrac{81}{16}$$ = $$250 imes81=Rs.$$ $$20,250$$ => Ans - (C)