GRE数学平均数问题备考解析
<p> 下面为大家介绍<span word="GRE">GRE</span>数学平均数考点。如果新<span word="GRE">GRE</span>数学考点都没有复习到，如何能拿到满意的<span word="GRE">GRE</span>数学分数呢?所以说，想要新<span word="GRE">GRE</span>数学考好，复习的时候一定要把新<span word="GRE">GRE</span>数学考点弄扎实。</p><p> <span word="Average">Average</span> <span word="of">of</span> <span word="n">n</span> <span word="numbers">numbers</span> <span word="of">of</span> <span word="arithmetic">arithmetic</span> <span word="progression">progression</span> <span word="is">is</span> <span word="the">the</span> <span word="average">average</span> <span word="of">of</span> <span word="the">the</span> <span word="smallest">smallest</span> <span word="and">and</span> <span word="the">the</span> <span word="largest">largest</span> <span word="number">number</span> <span word="of">of</span> <span word="them">them</span>. <span word="The">The</span> <span word="average">average</span> <span word="of">of</span> <span word="m">m</span> <span word="number">number</span> <span word="can">can</span> <span word="also">also</span> <span word="be">be</span> <span word="written">written</span> <span word="as">as</span> <span word="x">x</span> + <span word="d">d</span>/2.</p><p> <span word="Example">Example</span>:</p><p> <span word="The">The</span> <span word="average">average</span> <span word="of">of</span> <span word="all">all</span> <span word="integers">integers</span> <span word="from">from</span> 1 <span word="to">to</span> 5 <span word="is">is</span> /2=3</p><p> <span word="The">The</span> <span word="average">average</span> <span word="of">of</span> <span word="all">all</span> <span word="odd">odd</span> <span word="numbers">numbers</span> <span word="from">from</span> 3 <span word="to">to</span> 3135 <span word="is">is</span> /2=1569</p><p> <span word="The">The</span> <span word="average">average</span> <span word="of">of</span> <span word="all">all</span> <span word="multiples">multiples</span> <span word="of">of</span> 7 <span word="from">from</span> 14 <span word="to">to</span> 126 <span word="is">is</span> /2=70</p><p> <span word="remember">remember</span>:</p><p> <span word="Make">Make</span> <span word="sure">sure</span> <span word="no">no</span> <span word="number">number</span> <span word="is">is</span> <span word="missing">missing</span> <span word="in">in</span> <span word="the">the</span> <span word="middle">middle</span>.</p><p> <span word="With">With</span> <span word="more">more</span> <span word="numbers">numbers</span>, <span word="average">average</span> <span word="of">of</span> <span word="an">an</span> <span word="ascending">ascending</span> <span word="AP">AP</span> <span word="increases">increases</span>.</p><p> <span word="With">With</span> <span word="more">more</span> <span word="numbers">numbers</span>, <span word="average">average</span> <span word="of">of</span> <span word="a">a</span> <span word="descending">descending</span> <span word="AP">AP</span> <span word="decreases">decreases</span>.</p><p> <span word="AP">AP</span>:<span word="numbers">numbers</span> <span word="from">from</span> <span word="sum">sum</span></p><p> <span word="given">given</span> <span word="the">the</span> <span word="sum">sum</span> <span word="s">s</span> <span word="of">of</span> <span word="m">m</span> <span word="numbers">numbers</span> <span word="of">of</span> <span word="an">an</span> <span word="AP">AP</span> <span word="with">with</span> <span word="constant">constant</span> <span word="increment">increment</span> <span word="d">d</span>, <span word="the">the</span> <span word="numbers">numbers</span> <span word="in">in</span> <span word="the">the</span> <span word="set">set</span> <span word="can">can</span> <span word="be">be</span> <span word="calculated">calculated</span> <span word="as">as</span> <span word="follows">follows</span>:</p><p> <span word="the">the</span> <span word="first">first</span> <span word="number">number</span> <span word="x">x</span> = <span word="s">s</span>/<span word="m">m</span> - <span word="d">d</span>/2,<span word="and">and</span> <span word="the">the</span> <span word="n">n</span>-<span word="th">th</span> <span word="number">number</span> <span word="is">is</span> <span word="s">s</span>/<span word="m">m</span> + <span word="d">d</span>/2.</p><p> <span word="Example">Example</span>:</p><p> <span word="if">if</span> <span word="the">the</span> <span word="sum">sum</span> <span word="of">of</span> 7 <span word="consecutive">consecutive</span> <span word="even">even</span> <span word="numbers">numbers</span> <span word="is">is</span> 70, <span word="then">then</span> <span word="the">the</span> <span word="first">first</span> <span word="number">number</span> <span word="x">x</span> = 70/7 - 2/2 = 10 - 6 = 4.</p><p> <span word="the">the</span> <span word="last">last</span> <span word="number">number</span> <span word="is">is</span> 70/7+2/2=10+6=16.<span word="the">the</span> <span word="set">set</span> <span word="is">is</span> <span word="the">the</span> <span word="even">even</span> <span word="numbers">numbers</span> <span word="from">from</span> 4 <span word="to">to</span> 16.</p>
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