急！！！麻烦解决下几道prepare数学题。。。

甜心俏女巫

1。A set of 15 different integers has a median of 25 and a range of 25.What is the greatest possible integer that could be in this set?
A.32 B.37 C.40 D.43 E.50

2. 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?
A 100% decrease B.50% decrease  C. 40% decrease
D.40% increase E.50% increase

3. In a survey of students, each student selected from a list of 12 songs the 2 songs that the student liked best. If each song was selected 4 times, how many students were surveyed?
A 96  B 48  C 32  D 24  E 18

辛苦各位啦！万分感谢。。。

zowenny

第一题 25，25，25，25，25，25，25，25，25，25，25，25，25，25，50

fay009

1楼的说错了哦。。

1。A set of 15 different integers has a median of 25 and a range of 25.What is the greatest possible integer that could be in this set?
A.32 B.37 C.40 D.43 E.50

选择43.因为是不同的数，所以不可能是1楼的说法。我是用排除法，排除了50之后看43行不行，发现可以。
43-25=18，然后这些数就是18，19，20，21，22，23，24，25……后面就随便什么到43

2. 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?
A 100% decrease B.50% decrease  C. 40% decrease
D.40% increase E.50% increase

这个列个方程就好了。

【更正更正！！ - - 谢谢楼下提醒。。是（根号2）-1，我没看清楚题目】
方程应该是 V=A*A/B
然后变成V=(?A*?A)/2B，所以?=根号2，所以答案应该是40那个。。。。。

3. In a survey of students, each student selected from a list of 12 songs the 2 songs that the student liked best. If each song was selected 4 times, how many students were surveyed?
A 96  B 48  C 32  D 24  E 18
这题还没有做过。。不懂得答案

zowenny

rt

zowenny

2楼第二题错误！ prep里我做过 根号2 减一 是百分之多少来着

zowenny

第3题嘛 12*4/2

fay009

谢谢哦~~我记得答案是40%的不知道怎么刚刚做成100%了。。原来忘记看了一个平方。。谢谢你


第二题

方程应该是 V=A*A/B
然后变成V=(?A*?A)/2B，所以?=根号2，所以答案应该是40那个。。。。。

Sharonluo33

我是刚刚开始做题的菜鸟，不值得自己的思路对否
和A的平方成正比，B成反比，应该写A#2/B,B变成2B,A-A的平方根。增长大概40%

zy02042

第3题是24么
每首歌都被选了4次，那么总共被选了4*12=48次。
一个小盆友一次只能选2首，所以 平均下有48/2=24 个人~~