(1/(1*3))+(1/(3*5))+(1/(5*7))+...(1/(47*49)).
(1/(1*3))+(1/(3*5))+(1/(5*7))+…(1/(47*49))．
<gadget id="calculator">1 / 49</gadget>
<output>1/49 = around 0.020408</output>

<gadget id="calculator">1 - (1/49)</gadget>
<output>48/49 = around 0.979592</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(48/49) * (1/2)</gadget>
<output>24/49 = around 0.489796</output>

<result>24/49 = around 0.489796</result>