两道GMATPREP题，谁能帮忙解释一下？！？！

iriszhou

1. 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%, which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

a. 100%increase b. 100%decrease c. 40%increase d.40%decrease e.50%increase

答案是c. 不懂呢...

2. A certain library assesses fines for overdue books as follow on the first day that a book is overdue, the total fine is $0.10, for each additional day that the book is overdue, the total fine is either increased by $0.30 or doubled, whichever results in the lesser amount, what is the total fine for a book on a fourth day it is due?

a. $1.00 b. $0.90 c.0.70 d. 0.80 e. 1.50

答案是c. 算的是$0.80

jht8341

第1题，A的平方=B，根号2和A的积德平方=2B，根号2=1.414，

第2题，第四天交罚款，延期是3天

maybolett

我也刚做了~~不懂楼上的第一题啊~~NN们来解释一下啊  谢谢啊

第2题意思就是说借书超过日期了 超过的第一天罚0.1 第2天开始罚的款的总额要么是前一天的+0.3要么是前一天的*2，取其中小的。

 所以第2天是0.2 第三天是0.4 第四天是0.7  因为如果是DOUBLED那么是0.8  但加0.3=0.7要小些  选小的

清茶兑水

第一题就是

某个比是A^2/ B

现在B上升了100%，想要原来的比例保持不变。

因为B成了原来的200%，所以A要变成原来的200% 的开方。 也就是原来的140%。也就是要上升40%。

mmicetea

第一题:某反应率与A的浓度的平方成正比,与B的浓度成反比。B的浓度增加100%后问A要怎么变才能保证反应率不变。