(9/((1/20)+(1/60)+(1/120)+(1/200)+...+(1/900))).
(9/((1/20)+(1/60)+(1/120)+(1/200)+…+(1/900)))．
<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">(1/10) * (9/10)</gadget>
<output>9/100 = around 0.09</output>

<gadget id="calculator">9 / (9/100)</gadget>
<output>100</output>

<result>100</result>