请教PREP上的几道数学题目。谢谢大家

grantchao

mm第一道题搞错了，找了一下原题应是：

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A certain office supply store stocks 2 sizes of self-stick notepads, each in 4 colors:  blue, green, yellow, or pink.  The store packs the notepads in packages that contain either 3 notepads of the same size and the same color or 3 notepads of the same size and of

3 different colors.  If the order in which the colors are packed is not considered, how many different packages of the types described above are possible?

 

 

(A)  6

(B)  8

(C)  16

(D)  24

(E)  32

颜色相同的2*4=8 颜色不同的2*4=8

相加为16，选c

[此贴子已经被作者于2009-3-18 14:22:18编辑过]

grantchao

第2题设X部门fulltime a人，parttime b人,Y部门fulltime c人，parttime d人

条件1说a/b < (a+c)/(b+d)    可推出a/b < c/d

第3题设每年长x,第4年底的高度为4+4x,第6年底的高度为4+6x,相差2x.

由题意2x/(4+4x) =1/5  可推出x=2/3