38. K=0.1-(0.1)^2，问x>0.05?
1) K>0.009/x
2) K<0.0009/x
我选D
K=0.1-(0.1)^2=0.1-0.01=0.09
1)K>0.009/x
x>0.009/k=0.1
X>0.1>0.05所以(1)足够
2) K<0.0009/x
x<0.0009/k
x<0.0009/0.09=0.01
x<0.01<0.05所以(2)足够回答
ANS: D
[确认] D
怎么会是d ，x 可以为负数吧？在1）中
30、一图给出，由矩形中间一点，（看似在纵向中线上，但题目未说明）向四顶点分别作连线。问其中一条连线的平方由其余三条平方的表示。（应该是老jj当初看的时候觉得太简单，结果问题就来了）
这道题怎么作呀？请指教。
28.10^50-74是一个整数，问以十为底表示的这个数共有几位？
选项以百位记：2**。46*。47*。49*。49*，也许是题意理解有误，我的第一题，死活没做出来。
什么叫以十为底？ 是不是不大对？
20.机井。 36个数，分四组，每组从1到9，取出一个数，问取出的是几？
a.取出后各个数和的unit digit是6
b.取出后所有数的和是176
选d
不对吧？ a 不充分。
DS. Farmers 种 C and S. every C costs $500 per acre, every S costs $100 per acre, 问种C cost how much in total:
A. total cost for C and S is 34100.
B. farmer has 100 acre C
My answer: C
光b 就充分了 应选b
right cylinder是什么意思？是指正圆柱吗（高和底直径相等）还是就是圆柱？
[em27]
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if x is nagetive number , it is less than 0.05 still sufficient
30.from the point in the middle of the rectangle ,make height to each line of it , set them a,b,c,d
also set line that link the middle point to each of the rectangle's point w,x,y,z
then we have
a^2+b^2=w^2
b^2+c^2=x^2
c^2+d^2=y^2
a^2+d^2=z^2
finally , we can get w^2=X^2-y^2+z^2
20. A is sufficient
since the sum of the number 1 to 9 is 45
as one number picked out , leaving the unit of the sum 6
only one situation , that is 9 is eliminated
last DC about farmer
I am with you
btw , about the right cylinder no idea ...
pls help
这题我还是觉得不对
38. K=0.1-(0.1)^2，问x>0.05?
1) K>0.009/x
2) K<0.0009/x
我选D
K=0.1-(0.1)^2=0.1-0.01=0.09
1)K>0.009/x
x>0.009/k=0.1
X>0.1>0.05所以(1)足够
2) K<0.0009/x
x<0.0009/k
x<0.0009/0.09=0.01
x<0.01<0.05所以(2)足够回答
ANS: D
[确认] D
我认为：
1)k>0.009/x
1>0.1/x
if x>0, x>0.1>0.05
if x<0, x不大于0.05
so a is not sufficient
does anybody agree with me?
