用最自然，最地道，最不拗口的方式:
1） 奥巴马是美国第几任总统？
2) 我们班级有20几个学生。
我想来想去，只能这么说：
1） What is the ordinality (或者 order) of Obama's Presidency?
How many presidents have there been before Obama? (没办法了，绕圈子说法）
2) Our class has 20 something students. (听上去很chinglish).
The size of our class is in the 20's. （也很绕圈子）
l**********9 发帖数: 716
2
What number president is Obama
There're over 20 students in my class
c****2 发帖数: 3640
3
Obama is president number what
There are 20-30 students in our class
