GMAT数学例题详解(四)
<p> <span word="GMAT">GMAT</span>思为大家整理了<span word="GMAT">GMAT</span>数学例题详解系列，供考生们参考，以下是详细内容。</p><p> 16、{<span word="x">x</span>,<span word="y">y</span>,<span word="z">z</span>}的<span word="subset">subset</span>是<span word="X">X</span>，<span word="Y">Y</span>，<span word="Z">Z</span>，<span word="XY">XY</span>，<span word="XZ">XZ</span>，<span word="YZ">YZ</span>，<span word="XYZ">XYZ</span>；问：{<span word="W">W</span>，<span word="X">X</span>，<span word="Y">Y</span>，<span word="Z">Z</span>}的所有<span word="subset">subset</span>中有多少含有<span word="W">W</span>？</p><p> 【答案】8</p><p> 【思路】穷举一下：<span word="W">W</span>,<span word="X">X</span>,<span word="Y">Y</span>,<span word="Z">Z</span>,<span word="WX">WX</span>,<span word="WY">WY</span>,<span word="WZ">WZ</span>,<span word="XY">XY</span>,<span word="XZ">XZ</span>,<span word="YZ">YZ</span>,<span word="WXY">WXY</span>,<span word="WXZ">WXZ</span>,<span word="WYZ">WYZ</span>,<span word="XYZ">XYZ</span>,<span word="WXYZ">WXYZ</span></p><p> 17、<span word="m">m</span> <span word="is">is</span> <span word="two">two</span> <span word="digit">digit</span> <span word="number">number</span> <span word="and">and</span> 2<span word="m">m</span> <span word="is">is</span> <span word="a">a</span> <span word="three">three</span> <span word="digit">digit</span> <span word="number">number</span>, <span word="what">what</span> <span word="is">is</span> <span word="the">the</span> <span word="unit">unit</span> <span word="digit">digit</span> <span word="of">of</span> <span word="m">m</span>?</p><p> （1）<span word="the">the</span> <span word="unit">unit</span> <span word="number">number</span> <span word="of">of</span> 2<span word="m">m</span> <span word="is">is</span> 4;</p><p> （2）<span word="the">the</span> <span word="unit">unit</span> <span word="number">number</span> <span word="of">of</span> <span word="m">m</span> <span word="is">is</span> <span word="the">the</span> <span word="same">same</span> <span word="as">as</span> <span word="the">the</span> <span word="tens">tens</span> <span word="number">number</span> <span word="of">of</span> 2<span word="m">m</span>；</p><p> 【答案】<span word="E">E</span></p><p> 【思路】（1）表示<span word="the">the</span> <span word="unit">unit</span> <span word="number">number</span> <span word="of">of</span> <span word="m">m</span>可以是2或7；</p><p> （2）没有去除任何可能，举例<span word="m">m</span>可以是64或87。</p><p> 18、<span word="A">A</span>，<span word="B">B</span>是0-9之间的正整数，且<span word="A">A</span>+<span word="B">B</span>=14，设<span word="x">x</span>=0.<span word="A">A</span>，<span word="y">y</span>=0.<span word="B">B</span>，问<span word="x">x</span>乘以<span word="y">y</span>的最大值是多少？</p><p> 【答案】0.49</p><p> 【思路】</p><p> 题目：<span word="x">x</span>+<span word="y">y</span>=1.4，求<span word="max">max</span></p><p> 提示：<span word="x">x</span>与<span word="y">y</span>相等时<span word="xy">xy</span>最大</p><p> 另一种思路：穷举</p><p> <span word="A">A</span>=5; <span word="B">B</span>=9</p><p> <span word="A">A</span>=6; <span word="B">B</span>=8</p><p> <span word="A">A</span>=7; <span word="B">B</span>=7</p><p> 0.45</p><p> 0.48</p><p> 0.49</p><p> 0.49是答案</p><p> 19、扔两个子（1-6），问面朝上的值相加9的的概率？</p>
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