(1/(1*2))+(1/(2*3))+(1/(3*4))+...+(1/(49*50)).
(1/(1*2))+(1/(2*3))+(1/(3*4))+…+(1/(49*50))．
<gadget id="calculator">1 / 50</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">1 - (1/50)</gadget>
<output>49/50 = around 0.98</output>

<result>49/50 = around 0.98</result>