请再看几道机警多谢

carolexl

1． K is a three digit integer, whose unit digit is not zero. What is the tens digit of K. (1) The tens digit of K + 9 is 3 (2) The tens digit of K + 4 is 2 Answer C. 答案是不是A？？ 2． is 1000 a factor of x? 1) 2000 is a factor of 4x 2)8 is a factor of x answer C 3． is x <0? 1. x^-2z? 我觉得是C (1). xyz=1 (2). xyz^2>1 KEY: e why not C? (as NOT is also an answer) 12． If x and y are positive integers such that x=8y+12,what is the greatest common divisor of x and y? 1) x=12u,where u is an integer 2) y=12z,where z is 解答：由题知: x=4(2y+3) 由(1)知: x=12u 则y=3k k is an integer. x=12(2k+1) 则x,y最大公因子不能确定. 由(2)知: y=12z 则x=12(6z+1) ,因此x,y的公因子是12。 这题我认为选Ban integer X的各位和是170. X=20^17-Y,问Y. 可选项是从53到6?

tongxun

1. A.
2. c
3. B
4.E
5. 5/12
6. 15.2%. There is an completed question in my "september maths conclusion" in the top of this fortum.
7. 1/4. The amount of hard books = that of soft book. 1/(1+3)=1/4
8. D. a number is divided by 12, this number must has 3 and 4 factors.

tongxun

9 . why c ? X^2 -Y^2=16, when y=3, x=5 or x=-5.
   answer is E.
10. a wrong question.
11.C.  we can get c>1
12. 12. this question is one of maths questions in OG.