(1/(1*2))+(1/(2*3))+(1/(3*4))+...+(1/(9*10)).
(1/(1*2))+(1/(2*3))+(1/(3*4))+…+(1/(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>

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