Calculation: (1/(2*4))+(1/(4*6))+(1/(6*8))+…+(1/(16*18))+(1/(18* 20)).
计算：(1/(2*4))+(1/(4*6))+(1/(6*8))+…+(1/(16*18))+(1/(18*20))．
<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">(1/2) * (9/20)</gadget>
<output>9/40 = around 0.225</output>

<result>9/40 = around 0.225</result>