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标题: 请教几个数学问题 [打印本页]

作者: ypl214    时间: 2010-7-21 13:04
标题: 请教几个数学问题
1For every positive integer n,the function h(n) is defined to be the product of all the even integers from 2 to n.If p is the smallest prime of h(100)+1,then p is
A   between 2 and 10
B between 10 and 20
C between 20 and 30
D between 30 and 40
E greater than 40
2  The rate of a certain reaction id directly proportional to the square of the chemical A present and inversely propotional to the concentration of chemical B present.If the concentration chemical B is increased by 100 percent,which of the following is closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

答案是40% increase
作者: ypl214    时间: 2010-7-21 17:23
顶一下 主要是第二个咋做
作者: mmyiru    时间: 2010-7-21 23:55
1. E

2. Let reaction rate be r, then r = A^2/B

如果分母增加为2B, 为了保证r不变,分子必须增加为 2*A^2 =(根号下2A)^2, 所以A必须从A增加为(根号下2)*A = 1.414 A. 也就是大概增加了40%
作者: ypl214    时间: 2010-7-22 08:57
多谢了




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