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  3. There is a four-digit number made with 1 -9! Its 2nd digit is twice greater than its 3rd. The sum of all the digits is thrice gr

There is a four-digit number made with 1 -9! Its 2nd digit is twice greater than its 3rd. The sum of all the digits is thrice gr

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问题 There is a four-digit number made with 1 -9! Its 2nd digit is twice greater than its 3rd.
The sum of all the digits is thrice greater than its last digit! The product of its 3rd and 4th digits is 12 times greater than the ratio of its 2nd to 3rd. What is it?
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答案7638
解析 (这是一个四位数，第二个是第三个的两倍，有四种可能，2，1；4，2；6，3；8，4；然后设第四个数为a，第一个数为b，那么先假设第二第三位数为2，1，则a=12*2=24>9，不符合，同理4，2也不符合，如果是6，3，则3a=12*2=24，a=8，8+6+3+b=8*3=24，b=7，则这个四位数为7638，如果是8，4，则4a=12*2=24，a=6，6+8+4+b=6*3=18，b=0<1，不符合，所以，答案为7638。)
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本试题收录于： C类竞赛（非英语专业本科）题库大学生英语竞赛（NECCS）分类
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C类竞赛（非英语专业本科）

大学生英语竞赛（NECCS）

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