(1/2)+(1/6)+(1/12)+...+(1/72)+(1/90).
(1/2)+(1/6)+(1/12)+…+(1/72)+(1/90)．
<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>

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