老牛本月4个数学题答案有错误(新)

qian800

96（PS）总共140张牌，数发给一群人。条件是超过2人，每人超过2张。问有几个可能？

选项里有排除掉不是140的约数后,有5和10这两个选项.觉得都对。然后猜了10（是正确的？？？？？）

选项里有排除掉不是140的约数后,有5和10这两个选项.觉得都对。然后猜了10（是正确的？？？？？）

条件是超过2人，每人超过2张，我回答：8

条件是最少2人，每人最少2张，我回答：10

93（DS）=130题
说一个有X个小正方体组成的长方体，如果用油漆涂他的表面，而油漆的价格是每单位Y cents（单位是乱编的），那么涂满长方体需要多少钱？（x，y均为数字）

1：告诉涂满所有小正方体表面的钱

2：x=2

机经是A，

关键是：不知道有几个相邻表面不需要油漆

前提是“油漆的价格是每单位Y cents”单位要明确，这样算出有几个小正方体，如果是6个以下则A成立，6个以上排列方法不同，A不成立

133（DS）2 t u是一个三位数， t和u分别为1到9之间的数。问2 + t + u 是否能被9整除.

1：u=9（不行）

1：u=9（不行）

2：t + u能被4（或者3）整除  (我回答E）

2：t + u能3整除（我回答B）

157（DS）2^x = ？

1：(2^x )²= 512 （不知道正负）

2：3^x= 1 / 27

机经主人选了B，我选D，2^x 能为负数吗？不能

[此贴子已经被作者于2009-1-28 2:19:50编辑过]

coldghost

93，本人也认为选c

wangxiaoqing

93（DS）=130题
    

说一个有X个小正方体组成的长方体，如果用油漆涂他的表面，而油漆的价格是每单位Y cents（单位是乱编的），那么涂满长方体需要多少钱？（x，y均为数字）
    

 1：告诉涂满所有小正方体表面的钱
   

2：x=2

机经是A，

我答C，否则不知道有几个相邻表面不需要油漆

前提是“油漆的价格是每单位Y cents”单位要明确，这样算出有几个小正方体，如果是6个以下则A成立，6个以上排列方法不同，A不成立

1: total expense is known, and we have a total of 6X faces, but we do not know X, so we do not know the expense of painting each face. And also we do not know how many faces (could be 8 or 9)to be painted. So A is not sufficient

2: 2 squares, 12 faces. But you got two ways to put the two squares. One way: you need to paint 8 faces. Another way: you need to paint 9 faces. So B is not good

1+2: total of 12 faces, total expenses to paint these 12 faces are known. Therefore, the expenses per face is known. But you could paint 9 faces or 8 faces. So 1+2 does not suffice.
Answer should be E

 You need the additional information of how to displace these 2 squares. Also, Y cents should be specified more clearly. I do not know whether Y cents are expenses for painting one square face or expense for one unit of paint. In the latter case, Y might be irrelevant.

wangxiaoqing

A mistake in 1: cross out "could be 8 or 9".

1: total
expense is known, and we have a total of 6X faces, but we do not know
X, so we do not know the expense of painting each face. And also we do
not know how many faces to be painted. So A is not
sufficient

coldghost

93, if both statements are together, cost = 10/12*"cost of all small cubid "

wangxiaoqing

I still think answer should be E because differences in how you put the squares really matter.

Consider: two squares next to each other on the same level (need to paint 8 faces).

Or: one square on top of the second one (need to paint 9 faces).

yzhao26

Given 说一个有27个小正方体组成的正方体(CUBE), so A is right

Please read Q130 carefully

wangxiaoqing

Given 说一个有27个小正方体组成的正方体(CUBE)

说一个有X个小正方体组成的长方体

maybe we are talking about two different questions

entheticism

有问题就好，最怕没问题。
多谢所有lz同学们的思路。

wangxiaoqing

1: total
expense is known, and we have a total of 6X faces, but we do not know
X, so we do not know the expense of painting each face. And also we do
not know how many faces to be painted. So A is not
sufficient

2: 2 squares, 12 faces. But you got two ways to put
the two squares. One way: you need to paint 8 faces. Another way: you
need to paint 9 faces. So B is not good

1+2: total of 12 faces,
total expenses to paint these 12 faces are known. Therefore, the
expenses per face is known. But you could paint 9 faces or 8 faces. So
1+2 does not suffice.
Answer should be E

 You need the
additional information of how to displace these 2 squares. Also, Y
cents should be specified more clearly. I do not know whether Y cents
are expenses for painting one square face or expense for one unit of
paint. In the latter case, Y might be irrelevant.