作者SONY (i still love ....)
看板GMAT
标题Re: [计量] GWD30-26.31
时间Tue Aug 11 23:06:19 2009
※ 引述《jjoosshh (joshchu)》之铭言：
: GWD30-26
: Is X<Y?
: (1) The ratio of x to y is 7/9
: (2) xy>0
(1) x/y = 7/9, 看的出x,y是同号
(a)如果x,y > 0 ---> (ex: x=7,y=9) x < y
(b)如果x,y < 0 ---> (ex: x=-7, y=-9) x > y
(2) xy > 0, 只表示x,y是同号而已, x,y各是多少完全不知
(1)+(2) x,y同号且有x/y=7/9的比例关系 ---> 等同於(1)的讨论,可能x>y 或是x<y
: Key: (E)
: GWD30-31
: There is 5 cars to displayed in 5 parking spaces with all the cars facing
: the same direction. Of the 5 cars, 3 are reds, 1 is blue, and 1 is yellow,
: and 1 is yellow. If the cars are identical except for color, how many
: different display arrangements of the 5 cars are possible?
: A. 20
: B. 25
: C. 40
: D. 60
: E. 125
: Key: (A)
3车是一模一样的红车, 1车蓝, 1车大黄蜂
想法是把5台车全混在一起排列, 然後再除掉3台红车的排列(因为这3台一模一样)
全部一起排列---> 5x4x3x2x1 = 120
3台红车排列---> 3x2x1 = 6
===> 所以120/6 = 20
: 谢谢解题!! Tkx...
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※ 编辑: SONY 来自: 140.112.4.234 (08/11 23:07)
1F：推 Astrogod:推大黄蜂... 08/11 23:10