Ramu borrowed some money from his friend at simple interest of 6% per annum. He returned his friend Rs. 15600. After how much time did Ramu return the money if he borrowed Rs. 12000?

5 years

According to the question:

Simple interest - 15600 - 12000 = 3600, ROI - 6%, Principle - 12000

Formulae for SI = \(\frac{\text{P Χ R Χ T} }{ 100}\) 

Putting the values in the formulae:

3600 = \(\frac{\text{12000 Χ 6% Χ T} }{ 100}\) 

3600 = 720T

T = \(\frac{ 3600}{720 }\)

T = 5

Thus, after 5 years Ramu returned the money which he borrowed.