Calculation: (1/(1+2))+(1/(1+2+3))+(1/(1+2+3+4))+…+(1/(1+2+3+ ...+19))=how much.
计算：(1/(1+2))+(1/(1+2+3))+(1/(1+2+3+4))+…+(1/(1+2+3+…+19))=多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/2) - (1/20)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">2 * (9/20)</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>