Calculation: (1/(1*2*3))+(1/(2*3*4))+…+(1/(20*21*22)).
计算：(1/(1*2*3))+(1/(2*3*4))+…+(1/(20*21*22))．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">21 * 22</gadget>
<output>462</output>

<gadget id="calculator">1 / 462</gadget>
<output>1/462 = around 0.002165</output>

<gadget id="calculator">(1/2) - (1/462)</gadget>
<output>115/231 = around 0.497835</output>

<gadget id="calculator">(1/2) * (115/231)</gadget>
<output>115/462 = around 0.248918</output>

<result>115/462 = around 0.248918</result>