gre数学：5道难题解答2
<p> 新版<span word="gre">gre</span>考试数学正在越来越难，这是由于美国数学基础教育的难度增加导致的，而改革后的新<span word="gre">gre</span>考试，更加注重考察考生的研究能力，同时在内容和形式上都有很大变化，出现了无选项计算题，这意味对考生解题思路要求提高了，所以不能对新<span word="gre">gre</span>考试数学掉以轻心。下面随小编为大家搜索整理的<span word="gre">gre</span>数学难题，考试之前预热一下吧：</p><p> 6.<span word="The">The</span> <span word="reflection">reflection</span> <span word="of">of</span> <span word="a">a</span> <span word="positive">positive</span> <span word="integer">integer</span> <span word="is">is</span> <span word="obtained">obtained</span> <span word="by">by</span> <span word="reversing">reversing</span> <span word="its">its</span> <span word="digits">digits</span>. <span word="For">For</span> <span word="example">example</span>, 321 <span word="is">is</span> <span word="the">the</span> <span word="reflection">reflection</span> <span word="of">of</span> 123. <span word="The">The</span> <span word="difference">difference</span> <span word="between">between</span> <span word="a">a</span> <span word="five">five</span>-<span word="digit">digit</span> <span word="integer">integer</span> <span word="and">and</span> <span word="its">its</span> <span word="reflection">reflection</span> <span word="must">must</span> <span word="be">be</span> <span word="divisible">divisible</span> <span word="by">by</span> <span word="which">which</span> <span word="of">of</span> <span word="the">the</span> <span word="following">following</span>?</p><p> <span word="A">A</span>. 2</p><p> <span word="B">B</span>. 4</p><p> <span word="C">C</span>. 5</p><p> <span word="D">D</span>. 6</p><p> <span word="E">E</span>. 9</p><p> 翻译：<span word="reflection">reflection</span> 被定义为把一个多位数的数字次序倒过来，组成新的一个数字，比如，321的<span word="reflection">reflection</span>就是123.那么一个五位数和其<span word="reflection">reflection</span>的差一定能被哪个数整除?</p><p> 解答：方法一，直接写一个数，比如 12345，那么它的<span word="reflection">reflection</span>为54321，差值为41976，排除<span word="C">C</span>，继续选数，12346，<span word="reflection">reflection</span>64321，差值51975，排除<span word="A">A</span>,<span word="B">B</span>,<span word="D">D</span>，选<span word="E">E</span></p><p> 方法二：设个十百千万上的数分别为<span word="a">a</span>,<span word="b">b</span>,<span word="c">c</span>,<span word="d">d</span>,<span word="e">e</span> 那么原数和<span word="reflection">reflection</span>分别为 10000<span word="a">a</span>+1000<span word="b">b</span>+100<span word="c">c</span>+10<span word="d">d</span>+<span word="e">e</span> 和 10000<span word="e">e</span>+1000<span word="d">d</span>+100<span word="c">c</span>+10<span word="b">b</span>+<span word="a">a</span> 差值为 9999<span word="a">a</span>+990<span word="b">b</span>- 990<span word="d">d</span>9999<span word="e">e</span>的绝对值很容易看出为9的倍数选择<span word="E">E</span></p>
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