If the price of petrol increases by 40, by how much must a user cut down his consumption so that his expenditure on petrol remains constant?
Choose the correct choice:
A) 25 %
B) 20 %
C) 16.67 %
D) 28.6 %
E) none of these

Rationale: "explanation : let us assume before increase the petrol will be rs . 100 . after increase it will be rs ( 100 + 40 ) i . e 140 . now , his consumption should be reduced to : - = ( 140 − 100 ) / 140 ∗ 100 . hence , the consumption should be reduced to 28.6 % . answer : d"
Answer: D