368.The rate of a certain chemical reaction is directly proportional to the square of the concentration of chemical A present and inversely proportional to the concentration of the chemical B present . If the concentration of chemical B is increased by 100 persent, which of the following is closest to the percent change in the concentration of chemical of A required to keep the reaction rate unchanged?

A 100% increase

B 50% decrease

C 40% decrease

D 40 % increase

E 50% increase

A 100% increase

B 50% decrease

C 40% decrease

D 40 % increase

E 50% increase

A 100% increase

B 50% decrease

C 40% decrease

D 40 % increase

E 50% increase

是不是选D啊,

题目说a certain chemical reaction(设为X)与A的平方成正比, 与B成反比, 根据题意可列方程,

x=(A的平方)/B

当B增加100%时, 方程变为(A的平方)/2B, 要使原来的方程不变, 那么分子就必须变为2*(A的平方) 因为

(1.4A)的平方=1.96(A的平方) 

问题是closest to the percent ,1.96 ≈   2, 所以选D