题库搜索>问题求解PS-13310
How many 4-digit positive integers are there in which all 4 digits are even?
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分析B选项
分析C选项
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四位数的每个位数都为偶数，除了首位其余可选0，2，4，6，8
首位可选2，4，6，8
答案即为：1C4*1C5*1C5*1C5=4*5*5*5=500
选择：C
244581ucnoy
又是题目没看明白做错了。我以为是问四位数里有多少个4位数是偶数的？其实题目是问4位数里，个十百千四位都是偶数的这样的数字有多少个？千位不能是0，只能有2468，其余百十个都是024685个选择，就是4*5*5*5=500
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2022-09-14 15:47:05
626617yh
0也是偶数， 4*5*5*5
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2021-03-28 20:13:32
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