Simple calculation: (2/(1*2))+(2/(2*3))+(2/(3*4))+…+(2/(9*10)).
简便计算：(2/(1*2))+(2/(2*3))+(2/(3*4))+…+(2/(9*10))．
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">2 * (9/10)</gadget>
<output>9/5 = around 1.8</output>

<result>9/5 = around 1.8</result>