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以下是引用wangxiaoqing在2009-1-26 5:31:00的发言：
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 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
How come there are two ways to arrange 2 squares?
I think that we just can connect the 2 squares so that there is only one way: 10 faces needed to paint.
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
If my way of thinking is right, (1)+(2) could solve the problem based on clear figure Y.
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.
[此贴子已经被作者于2009-1-26 16:30:20编辑过] | 
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发表于 2009-1-26 06:05:00
