Calculation: (1/(2004*2005))+(1/(2005*2006))+(1/(2006*2007))+(1/(2007*2008))+(1/(2008*2009) )+(1/2009).
计算：(1/(2004*2005))+(1/(2005*2006))+(1/(2006*2007))+(1/(2007*2008))+(1/(2008*2009))+(1/2009)．
<gadget id="calculator">2_004 * 2_005</gadget>
<output>4_018_020</output>

<gadget id="calculator">1 / 4_018_020</gadget>
<output>1/4_018_020 = around 0</output>

<gadget id="calculator">2_005 * 2_006</gadget>
<output>4_022_030</output>

<gadget id="calculator">1 / 4_022_030</gadget>
<output>1/4_022_030 = around 0</output>

<gadget id="calculator">2_006 * 2_007</gadget>
<output>4_026_042</output>

<gadget id="calculator">1 / 4_026_042</gadget>
<output>1/4_026_042 = around 0</output>

<gadget id="calculator">2_007 * 2_008</gadget>
<output>4_030_056</output>

<gadget id="calculator">1 / 4_030_056</gadget>
<output>1/4_030_056 = around 0</output>

<gadget id="calculator">2_008 * 2_009</gadget>
<output>4_034_072</output>

<gadget id="calculator">1 / 4_034_072</gadget>
<output>1/4_034_072 = around 0</output>

<gadget id="calculator">1 / 2_009</gadget>
<output>1/2_009 = around 0.000498</output>

<gadget id="calculator">(1/4_018_020) + (1/4_022_030) + (1/4_026_042) + (1/4_030_056) + (1/4_034_072) + (1/2_009)</gadget>
<output>1/2_004 = around 0.000499</output>

<result>1/2_004 = around 0.000499</result>