Question

In what time will Rs. 1000 amount to Rs. 1331 at $10\%$ per annum compound interest.

Answer 1

Given,

Principal (P) = Rs. 1000
Amount (A) = Rs. 1331
Rate (R) $=10\%$ p.a
Let period = n year
Then $\frac{A}{P}={(1+\frac{R}{100})}^n$
$\Rightarrow \frac{1331}{1000}={(1+\frac{10}{100})}^n$
$\Rightarrow \frac{1331}{1000}={\left(\frac{11}{10}\right)}^n\Rightarrow {\left(\frac{11}{10}\right)}^3={\left(\frac{11}{10}\right)}^n$
Comparing, we get:
n = 3
$\therefore$ Period = 3 years.