Calculation: (2/(2*3))+(2/(3*4))+(2/(4*5))+...+(2/(139*140)).
计算：(2/(2*3))+(2/(3*4))+(2/(4*5))+…+(2/(139*140))．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 140</gadget>
<output>1/140 = around 0.007143</output>

<gadget id="calculator">(1/2) - (1/140)</gadget>
<output>69/140 = around 0.492857</output>

<gadget id="calculator">2 * (69/140)</gadget>
<output>69/70 = around 0.985714</output>

<result>69/70 = around 0.985714</result>