. Law of Variable Proportions is valid when

A: Only one input is varied and all other inputs are kept constant

B: All Factors are kept constant

C: All inputs are varied in the same proportion

D: Any of the above


Best Answer


  • The law of variable proportions, an essential economic concept,

states that an increase in a particular factor of production,

while all others are constant, will cause the marginal product to eventually decline. 

  • The following diagram depicts the law of variable proportions:


Here, TPP is the abbreviation for the total physical product and MPP is the abbreviation for marginal physical product.

Final Answer:

Hence, the correct answer is option A: Only one input is varied, and all other inputs are kept constant.



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