AMC 8 1990 Problem 12

AMC8 1990 年第 12 题

排列与组合★★★☆☆

There are twenty-four 4-digit numbers that use each of the four digits 2, 4, 5, and 7 exactly once. Listed in numerical order from smallest to largest, the number in the

17\textth

position in the list is

用数字 2、4、5、7 各用一次组成的四位数共有二十四个。按从小到大的顺序排列，第 17 个数是

A.4527
B.5724
C.5742
D.7245
E.7524

正确答案 · Correct Answer

解析 · Solution

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