(1/(1*2*3))+(1/(2*3*4))+...+(1/(98*99*100)).
(1/(1*2*3))+(1/(2*3*4))+…+(1/(98*99*100))．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">99 * 100</gadget>
<output>9_900</output>

<gadget id="calculator">1 / 9_900</gadget>
<output>1/9_900 = around 0.000101</output>

<gadget id="calculator">(1/2) - (1/9_900)</gadget>
<output>4_949/9_900 = around 0.499899</output>

<gadget id="calculator">(1/2) * (4_949/9_900)</gadget>
<output>4_949/19_800 = around 0.249949</output>

<result>4_949/19_800 = around 0.249949</result>