求教一道数学题

xiaochangshni

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 chemical B present. If the concentration of chemical B is increased by 100 percent, which of the following is closet to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

100% decrease

50% decrease

40% decrease

40% increase

50% increase

tonger

D 1.4*1.4=1.96约等于2

fankser

这题我也很纠结.........明明应该是INCREASE 100%啊........

tonger

to the square of the concentration of chemical A  请注意这句话 是平方

pite82

and inversely proportional 这表示什么意思? 表达不清楚.

joanjoans

The rate of a certain chemical reaction与  A²与正比，与B成反比；既然B增加了100%即变为原来的2倍，那说明The rate of a certain chemical reaction就减少了变为原来的2分之1，就说明A必然要减少；但题目要求The rate of a certain chemical reaction不变，这就要求A²要变为原来的2倍，即A只能增加，增加的量是A²*（1+x）²= 2A²的解