2003 AMC 10A 第 15 题

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所有题目均经美国数学协会(MAA)官方合法授权使用。

15.

从集合 {1,2,3,,100}\{1, 2, 3, \ldots, 100\} 中随机选一个整数,它能被 22 整除但不能被 33 整除的概率是多少?

What is the probability that an integer in the set {1,2,3,,100}\{1, 2, 3, \ldots, 100\} is divisible by 22 and not divisible by 3?3?

16\dfrac{1}{6}

33100\dfrac{33}{100}

1750\dfrac{17}{50}

12\dfrac{1}{2}

1825\dfrac{18}{25}

答案:C
知识点:基本概率倍数区间内整数计数
难度评级:1310
解答:

100100 个整数中有 5050 个能被 22 整除。

其中同时能被 33 整除的是 66 的倍数,共 1616 个。

因此符合条件的数有 5016=3450 - 16 = 34 个,概率为 34100=1750\dfrac{34}{100} = \dfrac{17}{50}

所以正确答案是 C

Of the 100100 integers, 5050 are divisible by 2.2.

Among those, the ones also divisible by 33 are the multiples of 6,6, of which there are 16.16.

So 5016=3450 - 16 = 34 qualify, giving probability 34100=1750.\dfrac{34}{100} = \dfrac{17}{50}.

Thus, the correct answer is C.

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