In how many years, The simple interest earned on Rs. 6000 at an interest rate of 5% per annum will be equal to simple interest earned on Rs. 2000 at the rate of 4% per annum for 30 years?

In the first case the principal amount, rate of interest, and time period are $$principal_1, rate_1, time_1$$

In the second case the principal amount, rate of interest, and time period are $$principal_2, rate_2, time_2$$

$$\frac{principal_1\times rate_{1\ }\times\ time_1\ }{100}\ =\ \frac{principal_2\times rate_{2\ }\times\ time_2\ }{100}$$

$$\frac{6000\times5\times time_1\ }{100}\ =\ \frac{2000\times4\times30\ }{100}$$

$$3\times5\times time_1\ \ =\ 1\times4\times30\ $$