Mohan borrowed an amount of Rs.18,000 and paid a simple interest of Rs.2,700 at 10% per annum. Find the duration for which he kept the borrowed amount. 

Principal, P = Rs.18000

Simple Interest, SI = Rs. 2700

Rate of Interest, R = 10 % per annum

​$$SI = \frac{P \times R \times T}{100}$$​​

Substitute the values in the formula;

​$$2700 = \frac{18000 \times 10 \times T}{100} \\ \ \\T = \frac{2700 \times 100}{18000 \times 10} \\ \ \\T = \frac{270000}{180000} = \frac{ 3}{2} \ \text{year} = 1.5 \text{ years}$$​​

Thus, Mohan kept the borrowed amount for $$\frac{ 3}{2} \ \text{year}$$ or  1.5 years.