gre数学基本概念及实例解析(7)
<p> <span word="gre">gre</span>数学考试在新<span word="gre">gre</span>考试当中增加了一些难度，但是<span word="gre">gre</span>考生也不要太紧张，只要把一些<span word="gre">gre</span>数学基本概念掌握好，解题时就一定能轻松应对。</p><p> 概率<span word="Probability">Probability</span></p><p> 某种特定要求的结果出现的概率=满足要求的结果总数/所有可能的结果数互斥事件<span word="Mutually">Mutually</span> <span word="exclusive">exclusive</span> <span word="events">events</span></p><p> 两个互斥事件同时发生的概率为0</p><p> 独立事件 <span word="Independent">Independent</span> <span word="events">events</span></p><p> 两个独立事件<span word="A">A</span>,<span word="B">B</span>同时发生的概率为<span word="AB">AB</span>各自单独发生的概率之乘积两个独立事件<span word="AB">AB</span>单独发生的概率分别为<span word="a">a</span>,<span word="b">b</span>,则<span word="AB">AB</span>之中至少发生一个的概率为：</p><p> <span word="a">a</span>+<span word="b">b</span>-<span word="ab">ab</span></p><p> 若某事件的完成可以分成<span word="n">n</span>个步骤，满足其第一步要求的概率是<span word="P">P</span>1，满足第二步的概率是<span word="P">P</span>2满足第<span word="n">n</span>步的概率是<span word="Pn">Pn</span>，那么最终结果达到要求的概率为<span word="P">P</span>=<span word="P">P</span>1<span word="P">P</span>2</p><p> 若某时间的完成可以通过<span word="n">n</span>种不同途径，通过第一种途径达到要求的概率是<span word="P">P</span>1，通过第二种途径达到要求的概率是<span word="P">P</span>2通过第<span word="n">n</span>种途径达到要求的概率是<span word="Pn">Pn</span>，那么最终结果达到要求的概率为<span word="P">P</span>=<span word="P">P</span>1+<span word="P">P</span>2++<span word="Pn">Pn</span></p><p> 例题.扔两次硬币，两次都得到正面的概率?两次都是同一面的概率?</p><p> 例题.100个零件里面有10个事坏的，从中随机取出3个，3个都是坏零件的概率是多少?</p><p> 例题.<span word="Cast">Cast</span> <span word="two">two</span> <span word="dices">dices</span> <span word="and">and</span> <span word="get">get</span> <span word="two">two</span> <span word="values">values</span>, <span word="what">what</span> <span word="is">is</span> <span word="the">the</span> <span word="probability">probability</span> <span word="of">of</span> <span word="one">one</span> <span word="value">value</span> <span word="being">being</span> <span word="exactly">exactly</span> 2 <span word="more">more</span> <span word="than">than</span> <span word="the">the</span> <span word="other">other</span>?</p>
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