Calculate (1/(1*2))+(1/(2*3))+(1/(3*4))+...+(1/(19*20)).
计算(1/(1*2))+(1/(2*3))+(1/(3*4))+…+(1/(19*20))．
<gadget id="calculator">1 / 1</gadget>
<output>1</output>

<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 - (1/20)</gadget>
<output>19/20 = around 0.95</output>

<result>19/20 = around 0.95</result>