GMAT数学例题及解析
<p> 一枚<span word="coin">coin</span>，投一次正面朝上的概率不是0.5，问是多少? (1)正面朝上是正面朝下的概率的两倍; (2)连续投两次，一次朝上一次朝下的概率是4/9; 【答案】<span word="A">A</span> 【思路】设朝上的概率为<span word="X">X</span>，那么朝下的概率为1-<span word="X">X</span>;(1)<span word="X">X</span>=2(1-<span word="X">X</span>)==<span word="X">X</span>=2/3 (2)<span word="C">C</span>(2 1)*<span word="X">X</span>*(1-<span word="X">X</span>)=4/9==<span word="X">X</span>=1/3 <span word="OR">OR</span> 2/3 4<span word="s">s</span>, 6<span word="j">j</span>从中挑取3个，至少有1个<span word="s">s</span>，问多少咱挑法? 【答案】100 【思路】至少有1个<span word="s">s</span>，只要把总数中减去一个<span word="S">S</span>也没有就可以了。<span word="C">C</span>(10 3)-<span word="C">C</span>(6 3) <span word="x">x</span>^3<span word="y">y</span> (1)根号<span word="x">x</span><span word="y">y</span> (2)<span word="x">x</span><span word="y">y</span> 【答案】<span word="E">E</span> 【思路】举反例：(1)<span word="X">X</span>=1/4 <span word="Y">Y</span>=1/3 <span word="AND">AND</span> <span word="X">X</span>=4 <span word="Y">Y</span>=1 (2)<span word="X">X</span>=2 <span word="Y">Y</span>=1 <span word="AND">AND</span> <span word="X">X</span>=-2 <span word="Y">Y</span>=-3 (1)+(2)：<span word="X">X</span>=4 <span word="Y">Y</span>=1 <span word="AND">AND</span> <span word="X">X</span>=1/4 <span word="Y">Y</span>=1/7 一个物体<span word="mass">mass</span>的1/81/7部分在水面上，问水上比水下<span word="range">range</span>是多少? 【答案】1/71/6 【思路】<span word="IF">IF</span> 水上部分为1/8，则水下为7/8，比为1/7;<span word="IF">IF</span>水上部分为1/7，则水下为6/7，比为1/6。所以范围为1/71/6 <span word="x">x</span>^3-<span word="x">x</span> = (<span word="x">x</span>-<span word="a">a</span>)(<span word="x">x</span>-<span word="b">b</span>)(<span word="x">x</span>-<span word="c">c</span>)，且<span word="ac">ac</span>，问<span word="b">b</span>= ? 【答案】0 【思路】<span word="x">x</span>^3-<span word="x">x</span>=(<span word="X">X</span>-1)<span word="X">X</span>(<span word="X">X</span>+1)=(<span word="x">x</span>-<span word="a">a</span>)(<span word="x">x</span>-<span word="b">b</span>)(<span word="x">x</span>-<span word="c">c</span>) ，又<span word="ac">ac</span> 则1-1。所以<span word="B">B</span>=0 以上就是<span word="GMAT">GMAT</span>数学练习题，考生可以通过本文中的练习备考<span word="GMAT">GMAT</span>数学。</p>
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