Calculation: (1/(2+4))+(1/(2+4+6))+(1/(2+4+6+8))+…+(1/(2+4+…+ 20)) = how much.
计算：(1/(2+4))+(1/(2+4+6))+(1/(2+4+6+8))+…+(1/(2+4+…+20))=多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 11</gadget>
<output>1/11 = around 0.090909</output>

<gadget id="calculator">(1/2) - (1/11)</gadget>
<output>9/22 = around 0.409091</output>

<result>9/22 = around 0.409091</result>