數學題中英文表達看不懂和一些問題 拜託指點

lokoolo

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 incrased by 100 percent, which of the following to the percent change in the concentration of chemical A required to keep the reaction rate unchanged? 問題一: 請問方程式怎麼列: y*B =A^2 ? 問題二: 可否中文簡單講一下題目的意思  答案是40% increase   2. if each term in the sum a1..+ an is either 7 or 77 and the sum equals 350, which of the following could be equal to n? 答:40 問題: why? 3.Of the 60 animals on a certain farm, 2/3 are either pigs or cows. how may of the animals are cows? (1) the far has more than twice as many cows as it has pigs (2) the far has more than 12 pigs..問題一: 這題請問是表達 其中40隻不是豬就是牛嗎? 再來 如果知道(1) 不就確定牛是40隻了 答案是c 怎麼想也想不透 4. how many off intergers are greater than the integer x and less than the interger y?  (1) there are 12 even intergers greater than x and less than y 答案是(b) 不知道為啥不是(d) 這第一個條件感覺可以阿 5. each of the students in a certain class received a single grade of P, F, or I, what percent of the student in the class were females? (1) of those who received a P, 40 percent were females. (2) of those who received either an F, or I, 80 percent were males 答案為 (e) 我覺得是(c) 再來 第二個選項表達的意思是: 得到F 或I的這兩群人同共百分之八十是男生嗎? 還是個別的百分八十?   先在此謝謝幫忙高手們指教! 鞠躬!

jesuisdesole

那个猪和牛的我昨天问过,http://forum.chasedream.com/dispbbs.asp?boardID=22&ID=329157&page=2

有个CDER讲的很明白

lokoolo

謝謝! 可以拜託大家幫忙其他題嗎? 後天就考了 謝謝!

doitnow

 if each term in the sum a1..+ an is either 7 or 77 and the sum equals 350, which of the following could be equal to n? 答:40 問題: why?

To make th sum 350, we need at least one 77. So enumerate all possiblities as below:

if there is only one 77, then we need 39 '7' to make the sum 350 -> n=40

if there is two 77, then we need 28 '7' -> n=30;

if there is three 77, then we need 17 '7' -> n=20;

if there is four 77, then we need 6 '7' -> n=10;

Make sense? Hopefully

[此贴子已经被作者于2008-6-15 10:01:19编辑过]

proudking

1、V=n*A^2/B

这里V为反应速度，n为常数，可以不用管。如果B变成2B（这怎么听着像骂人），则为了保持V不变A必须变成根号2×A。根号2=1.414，所以是40%。

题目的意思是某化学反应速度和A的平方成正比，和B成反比。想保持化学反应速度不变。

2、本题你可以简化成 某数列，只包含 1或者11， 数列总和为50（所有相关数字全部除以7，关系不变）。这时候问一共“可能”（请注意是可能）有多少个数字。如果有39个1，1个11，总和就是50，故可能有40个数字。

3、别人讲过了，讲的很详细

4、举例说明。x、y两个数字。有一个偶数在它们之间，假设这个偶数是2，那么x=1，y=3，满足条件，x=0，y=4，同样满足，那么x、y之间可能有1个数，也可能有3个数。

5、拿P的人的总数X， 和拿F I的总人数 Y ，X、Y之间的比例关系不知道，没法算。你觉得能算，那请问结果是什么？

我也快考了，加油，共勉！

lokoolo

謝謝! 很清楚! 祝你門考牛分!