09月数学试题讨论稿第九篇（279--305）
<p> 279发行10种不同的邮票，某人有其中的3种。现从这10种中任选2种，问<span word="neither">neither</span> <span word="of">of</span> <span word="the">the</span> 2 <span word="stamps">stamps</span>不在某人所有的3种之内的可能性 ? 答案：<span word="C">C</span>/<span word="C">C</span>=7/15</p><p> 280. <span word="is">is</span> <span word="x">x</span>^2<span word="Y">Y</span>^2?</p><p> <span word="x">x</span>0。 答案：<span word="E">E</span></p><p> 281、=210^<span word="t">t</span>，要求用<span word="k">k</span>、<span word="m">m</span>表示<span word="t">t</span> 答案：<span word="k">k</span>+<span word="m">m</span>+1</p><p> =210^<span word="t">t</span>, 10<span word="K">K</span>+<span word="M">M</span>+1=10<span word="T">T</span></p><p> 282、直线<span word="l">l</span>，<span word="y">y</span>轴截距2，<span word="x">x</span>轴截距-3，问与<span word="l">l</span>平行的直线 ? 答案：3<span word="y">y</span>-2<span word="x">x</span>=0 同254</p><p> 283、<span word="GWD">GWD</span>那道拥有计算机的家庭比例题，答案50%</p><p> 同304题</p><p> 感谢<span word="ESeraph">ESeraph</span>的补充：</p><p> <span word="Of">Of</span> <span word="the">the</span> <span word="families">families</span> <span word="in">in</span> <span word="City">City</span> <span word="X">X</span> <span word="in">in</span> 1994, 40 <span word="percent">percent</span> <span word="owned">owned</span> <span word="a">a</span> <span word="personal">personal</span> <span word="computer">computer</span>. <span word="The">The</span> <span word="number">number</span> <span word="of">of</span> <span word="families">families</span> <span word="in">in</span> <span word="City">City</span> <span word="X">X</span> <span word="owning">owning</span></p><p> <span word="a">a</span> <span word="computer">computer</span> <span word="in">in</span> 1998 <span word="was">was</span> 30 <span word="percent">percent</span> <span word="greater">greater</span> <span word="than">than</span> <span word="it">it</span> <span word="was">was</span> <span word="in">in</span> 1994, <span word="and">and</span> <span word="the">the</span> <span word="total">total</span> <span word="number">number</span> <span word="of">of</span> <span word="families">families</span> <span word="in">in</span></p><p> <span word="City">City</span> <span word="X">X</span> <span word="was">was</span> 4 <span word="percent">percent</span> <span word="greater">greater</span> <span word="in">in</span> 1998 <span word="than">than</span> <span word="it">it</span> <span word="was">was</span> <span word="in">in</span> 1994. <span word="What">What</span> <span word="percent">percent</span> <span word="of">of</span> <span word="the">the</span> <span word="families">families</span> <span word="in">in</span> <span word="City">City</span> <span word="X">X</span> <span word="owned">owned</span> <span word="a">a</span> <span word="personal">personal</span> <span word="computer">computer</span> <span word="in">in</span> 1998?</p><p> <span word="A">A</span>. 50%</p><p> <span word="B">B</span>. 52%</p><p> <span word="C">C</span>. 56%</p><p> <span word="D">D</span>. 70%</p><p> <span word="E">E</span>. 74%</p><p> 284、从6个人中挑3个人组成<span word="committee">committee</span>，问有多少种可能? 答案：<span word="C">C</span>=20</p><p> 285、<span word="f">f</span>=<span word="x">x</span>-1/<span word="x">x</span>，问下面哪一个等于<span word="f">f</span>? 答案：<span word="f">f</span></p><p> 同225 第2次出现</p><p> 286、一个集合由44到54的连续整数 第组成，问随机挑出一个数字，能被7整除的概率 答案：只有49可以被7整除，所以<span word="P">P</span>=1/11</p>
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