2,5,4,9,3五个数任选3个数能组多少个不同和值的3位数

2025-04-17 17:38:45
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回答1:

既然是3的倍数,那么这个数必须是各位数加起来是3的倍数,所以如下:一位:3两位:12,15,21,24,42,51三位:123,135,132,153,213,231,234,243,345,354,423,432,435,453,543,534四位:1245,1254,1425,1452,1524,1542,2145,2154,2415,2451,2514,2541,4125,4152,4215,4251,5124,5142,5214,5241共43个