Ans: The Law of Variable Proportions is also popularly known as the Law of Diminishing Returns. According to this law, when one of the inputs involved in the production is changed while keeping the other inputs constant, there will be a point after which the output per unit of that particular input will start to decrease.  This law is theorized under certain assumptions. i) The technology should remain the same. ii) Some inputs should be kept constant iii) The possibility that the factors of production can be changed within a short period.