几道数学题目求解，感谢感谢。

luckyhaohuan

1.On a given day, 50 people took a test that is designed to measure a candidate’s aptitude. Some of the 50 people will take the test in the morning, and the remaining of the 50 people will take the test in the afternoon. What is the average (arithmetic mean) score on the test for the 50 examinees?
答案是E。为什么？
2.If $1,000 will be deposited in a bank account and I is the dollar amount of interest earned from the original deposit, represented as , and the annual interest rate is r percent, is r ＞ 8 percent?

(1) The deposit earns a total of $210 in interest in the first 2 years.

(2) （1+r/100)^2>1.15
答案是A，为什么？
3.
Each person who attended a company meeting was either a stockholder in the company, an employee of the company, or both. If 62 percent of those who attended the meeting were stockholders and 47 percent were employees, what percent were stockholders, who were not employees?
答案是C，怎么做啊？
If x,y ,and z are positive integers,is xz even?
(1)xy is even.
(2)yz is even.
答案是E，求解答。
上面所有的问题的答案都是题目给的答案，我也不懂对还是错，求解释，感谢感谢。

shangcailanru

我来试试，第一题没办法好像题都没给完
第二题也很奇怪 那个I 是什么？ 不过1中 利息=1000(r+1)r+1000r=210 可以算出 R=10%   2中直接用{-b-根号(b^2-4ac)}/2a 算出R就行了 反正不对
第三题 楼主也没给选项  62%+47%-1=19% 这19%就是既是S也是E的 所以 62%-19%就行了 不知道对不对
第四题
1中 XY是偶数的话 就是XY一奇一偶 或者两偶  2中同理 YZ一奇一偶或者两偶
当X时奇数的时候 Y就是偶数（根据1） 所以Z可以是奇数可以是偶数（满足2） 所以XZ奇偶不确定！
不知道对不对 楼主

luckyhaohuan

感谢感谢。