Gopi borrowed certain sum at the rate of 7% p.a. for the first 2 years, 9% p.a. for next 3 years and 13% p.a. for the period beyond 5 yrs. He paid an interest of Rs. 18600 for 9 years. Find the principal borrowed by him

To find the principal borrowed by Gopi, we can use the concept of compound interest.

Let's assume the principal borrowed by Gopi is P.

For the first 2 years, the interest rate is 7% per annum. So, the interest for the first 2 years would be (P * 7/100 * 2).

For the next 3 years, the interest rate is 9% per annum. So, the interest for the next 3 years would be (P * 9/100 * 3).

For the remaining 4 years (9 years - 2 years - 3 years), the interest rate is 13% per annum. So, the interest for the remaining 4 years would be (P * 13/100 * 4).

According to the given information, the total interest paid by Gopi for 9 years is Rs. 18600.

Therefore, we can write the equation as: (P * 7/100 * 2) + (P * 9/100 * 3) + (P * 13/100 * 4) = 18600

Simplifying the equation, we get: (14P/100) + (27P/100) + (52P/100) = 18600

Combining like terms, we have: (93P/100) = 18600

To solve for P, we can multiply both sides of the equation by (100/93): P = (18600 * 100) / 93

Calculating this, we find that the principal borrowed by Gopi is approximately Rs. 20000.