AMC 8 2001 Problem 24
AMC8 2001 年第 24 题
基本计数原理★★★★☆
Each half of this figure is composed of 3 red triangles, 5 blue triangles and 8 white triangles. When the upper half is folded down over the centerline, 2 pairs of red triangles coincide, as do 3 pairs of blue triangles. There are 2 red-white pairs. How many white pairs coincide?
该图形的每一半由 3 个红色三角形、5 个蓝色三角形和 8 个白色三角形组成。当上半部分沿中心线向下折叠时，2 对红色三角形重合，3 对蓝色三角形重合。还有两对红－白对。那么有多少对白色三角形重合？ Problem 25 There are 24 four-digit whole numbers that use each of the four digits 2, 4, 5 and 7 exactly once. Only one of these four-digit numbers is a multiple of another one. Which of the following is it? 2、4、5 和 7 这四个数字每个恰好使用一次，一共可以组成 24 个四位整数。这 24 个四位整数中，只有一个是另一个的倍数。则这个数是下列哪一个？
- A.4
- B.5
- C.6
- D.7
- E.9
正确答案 · Correct Answer
B
解析 · Solution
解析整理中
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