问三道prep的数学题

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

这一题的题干都看得我晕晕乎乎的，有人可以稍稍解释一下吗？谢谢

2.       If 100, then the greatest possible value of x is between

结果是3 and 6，但是我觉得这是x^2与y^2的圆的方程式啊，那不就是0<x^2<10吗？然后推出0<x<3.--, 不知道结果是怎么出来的。

3.       What is the remainder when the positive integer x is divided by 6?

(1)     When x is divided by 2, the remainder is 1, and when x is divided by 3, the remainder is 0.

(2)     When x is divided by 12, the remainder is 3.

这个integer被除余数的也搞不懂，答案是Each alone is sufficient.

谢谢大家，18号考试，也祝大家考试顺利！

还有一道啊，呵呵

1.       Last month 15 homes were sold in Town X, the average sale price of the homes was $150,000 and the median sale price was $130,000. Which is the following statements must be true?

At least one of the homes was sold for more than $165,000.

At least one of the homes was sold for more than $130,000 and less than $150,000.

At least one of the homes was sold for less than $130,000.

不管怎么样，那个165,000和130，000是怎么出来的呢？谢谢！！

3.(1)可以假设那个数是3（2t+1）   所以那个REMAIDER 就是1  

 （2）同理12t+3   也是这个道理  REMAIDER就是3了

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 closest to the percent change in the concentration of chemical A required to keep the reaction rate unchanged?

一种化学反应的速率是和A的占比的平方正相关，和B的占比负相关。如果B的量涨了100%，那么A的量需要怎么变化才能保证反应的速率不发生变化

Last month 15 homes were sold in Town X, the average sale price of the homes was $150,000 and the median sale price was $130,000. Which is the following statements must be true?

1.At least one of the homes was sold for more than $165,000.

2.At least one of the homes was sold for more than $130,000 and less than $150,000.

3.At least one of the homes was sold for less than $130,000.

这个平均价格是150，中位数是130

所以：

1.对，因为中位数比平均数低了20，所以肯定有数要来弥补这个20，也就是170，这个数是大于165的

2.错，因为130和150之间也许更本就没有数字。例如8个130，6个170，1个190就满足中位数130，平均数150

3.错，参考2

1.At least one of the homes was sold for more than $165,000.

2.At least one of the homes was sold for more than $130,000 and less than $150,000.

3.At least one of the homes was sold for less than $130,000.

这个平均价格是150，中位数是130

所以：

1.对，因为中位数比平均数低了20，所以肯定有数要来弥补这个20，也就是170，这个数是大于165的

2.错，因为130和150之间也许更本就没有数字。例如8个130，6个170，1个190就满足中位数130，平均数150

3.错，参考2