谢谢tongxun!
不过我是超菜(模考math75分钟从来没做完过,一般是41-44,不知到有没有跟我一样的?)
还得请较:
15.每个卖1.5,X个共收入1.5X
成本每个0.6,X个共花0.6X,设备投入和成本应该是0.6X+9900呀?
另外有几题,也请帮帮手:
58.6个数,从中拿2个,和是8,问拿到5的概率;
【确认】2/5
我的理解:(1,7);(2,6);(3,5);(4,4);(5,3);(6,2);(7,1)
概率为2/7呀?
115.a1=2, a2=3,the succeeding one is equal to the sum of all preceeding ones.
Supposing h and k denote 20th and 24th items, respectively, what is the
value of k/h.
choices: A.4 B. 8 C.10 D.16 E. 24.
【 确认】:d
我死活推不出公式来总不能硬算到20th,24th吧?
215。st不等于0,s-1/s<1/t-t,s-t>0?
1) s>1
2) t>0
【 确认】: a 原作者c
这道题代入后能明白。除了代入,能用式子推出来吗?作者: skycrash 时间: 2002-11-8 05:03
s>1 --> s-1 >0 --> s-1/s>0 --> 1/t-t>0 -->t<1/t -->t<1
so 1)s>t is sufficient
2) t>0 for example t=1/3 s=1/5 1/5 - 5 < 3-1/3
t=3 s=5 5-1/5 > 1/3 -3
so can't prove anything.
my answer is A.作者: cxh0798032 时间: 2002-11-8 15:12
140.A q for median, 97 students take apart in a test and the median score is 85 which of the following descriptions is correct? ;;;
1)At least 49 students’score are equal to or more than 85
2) At least 49 students’score are less than 85
3)At most 49 students’score are equal to or more than 85
【确定】3
这题应该是1)
193.X的平方+X=Y, ;;求下列哪一项必为偶数?
A X+Y B 2X+Y C X的平方+Y D XY+Y
【确定】 D.( 别背答案,其他三项不准,总之不对.)