Re: [計量] PP3的題目
※ 引述《volvox (╮(﹀_﹀")╭)》之銘言：
: The "reflection" of a positive integer is obtained by reversing its digits.
: For example, 321 is the reflection of 123. The difference between a
: five-digit integer and its reflection must be divisible by which of the
: following?
: (A) 2 (B) 4 (C) 5 (D) 6 (E) 9
: 我算出來結果是答案A和答案E都可以
: 因為差值是偶數 所以我就選了A 結果答案是E
: 我的算法是54321-12345=41976
: 請問各位版友 我是哪裡算錯了呢?
: 謝謝
五位數abcde
10000a+1000b+100c+10d+e -10000e-1000d-100c-10b-a
=9999a+990b-990d-9999e = 9(1111a+110b-110d-1111e)
所以9一定對
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