In how much time (in years) would Rs. 80,000 amounts to Rs. 1,17,128 at 10% per annum rate of interest, compounded yearly?

Correct option is A

Given:
Principal (P) = ₹80,000
Amount (A) = ₹1,17,128
Rate of interest (r) = 10% per annum
Formula Used:

$$A = P \left( 1 + \frac{r}{100} \right)^t\\$$ 

A = Amount
P = Principal amount
r = Rate of interest
n = Time

Solution:

$$1,17,128 = 80,000 \left( 1 + \frac{10}{100} \right)^t \\\frac{1,17,128}{80,000} = \left( 1 + \frac{10}{100} \right)^t \\\frac{1,17,128}{80,000} = \left( \frac{11}{10} \right)^t\\\left( \frac{11}{10} \right)^t = \frac{14,641}{10,000} \\\left( \frac{11}{10} \right)^t = \left( \frac{11}{10} \right)^4 \\t = 4 \, \text{years}$$​