Answer : 1. "8000"
Explanation :

To find the amount Imran borrowed, let's break down the problem step by step.

Let's denote the principal amount borrowed by Imran as P.

For the first four years, the simple interest is calculated at the rate of 8% per annum. So, the interest for the first four years = P * 8% * 4 = 0.08P * 4 = 0.32P

For the next six years, the simple interest is calculated at the rate of 10% per annum. So, the interest for the next six years = P * 10% * 6 = 0.1P * 6 = 0.6P

For the remaining five years (15 years total - 4 years - 6 years = 5 years), the simple interest is calculated at the rate of 12% per annum. So, the interest for the remaining five years = P * 12% * 5 = 0.12P * 5 = 0.6P

The total interest paid by Imran is given as Rs. 12,160.

So, adding up the interest for each period:

Total interest = 0.32P + 0.6P + 0.6P = 1.52P

Given that the total interest is Rs. 12,160, we can set up the equation:

1.52P = 12,160

Now, solve for P:

P = 12,160 / 1.52 P = 8,000

Therefore, Imran borrowed Rs. 8,000.