There has been successive increases of 25% and then 15% in the price of gas from the previous month. By what percentage should a driver reduce gas consumption so that the expenditure does not change?  Choose the correct choice from the following choices:
A) 30 %
B) 50 %
C) 66.66 %
D) 15 %
E) 75 %

Rationale: let p be the original price per unit of gas . let x be the original gas consumption . let y be the reduced gas consumption . y * 1.15 * 1.25 * p = x * p y = x / ( 1.15 * 1.25 ) which is about 0.7 x which is a decrease of about 30 % . the answer is a .
Answer: A