Q. At what percent per annum will Rs. 3000/- amounts to Rs. 3993/- in 3 years if the interest is compounded annually?
Answer: 10%
Notes: P = Rs. 3000 , A = Rs. 3993 , n = 3 years
$latex A = p \left ( 1+\frac{r}{100} \right )^{n}&s=1$
$latex \therefore \left ( 1 + \frac{r}{100} \right )^{n} = \frac{A}{P}&s=1$
$latex =>\left ( 1+\frac{r}{100} \right )^{3} = \frac{3993}{3000} = \frac{1331}{1000}&s=1$
$latex =>\left ( 1+\frac{r}{100} \right )^{3} = \left ( \frac{11}{10} \right )^{3}&s=1$
$latex =>1+\frac{r}{100} = \frac{11}{10}&s=1$
$latex =>\frac{r}{100} = \frac{11}{10}-1&s=1$
$latex => \frac{r}{100} = \frac{1}{10}&s=1$
$latex => r = \frac{100}{10} = 10\%&s=1$
Hence option [B] is the right ansewr.
