(1/(1990*1992))+(1/(1992*1994))+(1/(1994*1996))+(1/(1996*1998))+(1/(1998*2000))= How many.
(1/(1990*1992))+(1/(1992*1994))+(1/(1994*1996))+(1/(1996*1998))+(1/(1998*2000))=多少．
<gadget id="calculator">1_990 * 1_992</gadget>
<output>3_964_080</output>

<gadget id="calculator">1 / 3_964_080</gadget>
<output>1/3_964_080 = around 0</output>

<gadget id="calculator">1_992 * 1_994</gadget>
<output>3_972_048</output>

<gadget id="calculator">1 / 3_972_048</gadget>
<output>1/3_972_048 = around 0</output>

<gadget id="calculator">1_994 * 1_996</gadget>
<output>3_980_024</output>

<gadget id="calculator">1 / 3_980_024</gadget>
<output>1/3_980_024 = around 0</output>

<gadget id="calculator">1_996 * 1_998</gadget>
<output>3_988_008</output>

<gadget id="calculator">1 / 3_988_008</gadget>
<output>1/3_988_008 = around 0</output>

<gadget id="calculator">1_998 * 2_000</gadget>
<output>3_996_000</output>

<gadget id="calculator">1 / 3_996_000</gadget>
<output>1/3_996_000 = around 0</output>

<gadget id="calculator">(1/3_964_080) + (1/3_972_048) + (1/3_980_024) + (1/3_988_008) + (1/3_996_000)</gadget>
<output>1/796_000 = around 0.000001</output>

<result>1/796_000 = around 0.000001</result>