Question

In what time will Rs 1000 amount to Rs 1331 at 10% per annum, compound interest?

Answer 1

Let the time be n years.
Then, 
\[A = P \left( 1 + \frac{10}{100} \right)^n \]
\[1, 331 = 1, 000 \left( 1 + \frac{10}{100} \right)^n \]
\[ \left( 1 . 1 \right)^n = \frac{1, 331}{1, 000}\]
\[ \left( 1 . 1 \right)^n = 1 . 331\]
\[ \left( 1 . 1 \right)^n = \left( 1 . 1 \right)^3 \]
On comparing both the sides, we get: 
n = 3
Thus, the required time is three years.