3道数学题请教大家：

1. R is the set of positive odd integers less than 50, and S is the set of the squares of the integers in R. How many elements does the intersection of R and S contain?
a.None b.2 c.4 d.5 e.7
答案c.4
请问是哪4个？为什么我算来算去只有3个。。。

2. A certain company retirement plan has a "rule of 70" provision that allows an employee to retire when the employee's age plus years of employment with the company total at least 70. In what year could a female employee hired in 1986 on her 32nd birthday first be eligible to retire under this provision?
a.2003 b.2004 c.2005 d.2006 e.2007
答案是c.2005
为什么怎么算都不满70？

3. On a scale that measures the intensity of a certain phonomoneon, a reading of n+1 corresponds to an intensity that is 10 times the intensity corresponding to a reading of n. On that scale, the intensity corresponding to a reading of 8 is how many times as great as the intensity corresponding to a reading of 3?
a.5 b.50 c.10的5次方 d.5的10次方
答案c.10的5次方
请问该题是什么意思？

谢谢！

1. S=1, 9, 25, 49 与 R intersect

2. 设x年，x年时她有 [32+(x-1986)] 岁，在那个company工作了 (x-1986) 年，两者相加 =70，就可以算出x=2005

3. 题目意思说scale的读数是(n+1)的时候某种phenomenon的强度是读数是(n)的时候的10倍，问读数是8的时候的强度是读数是3的时候的几倍？   (8)=10(7)=10^2(6)=10^3(5)=10^4(4)=10^5(3)            括号里的是读数