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标题: GWD-MATH10-2,10 [打印本页]

作者: piqiuwawa 时间: 2005-8-26 06:31 标题: GWD-MATH10-2,10

2. A certain roller coaster has 3 cars, and a passenger is wqually likely to ride in any 1 of the 3 cars each time that passenger rides the roller coaster. If a certain passenger is to ride the roller coaster 3 times, what is the probability that the passenger will ride in each of the 3 cars?

B. 1/9

C. 2/9

C is correct, why not B?

10.a set of numbers has the property that for any number t in the set, t+2 is in the set. If -1 is in the set, which of the following must also be in the set?

I. -3

II. 1

III. 5

the answer is II and III only. why -3 is not in the set? It just said -1 is in the set, not said that -1 is the minimum, or we should think that -1 is the smallest number in the set? thanks

作者: himba 时间: 2005-8-26 12:40

1、P(3,3)/3^3＝2/9。首先分母表示总的可能数3×3×3；分子表示每次选一辆车的排列数。
2、你不能想当然。题目说了是t＋2，就只能往上加。

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