(1/4)+(1/8)+(1/16)+...+(1/256)+(1/512)=how much.
(1/4)+(1/8)+(1/16)+…+(1/256)+(1/512)=多少．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 / 512</gadget>
<output>1/512 = around 0.001953</output>

<gadget id="calculator">(1/2) - (1/512)</gadget>
<output>255/512 = around 0.498047</output>

<result>255/512 = around 0.498047</result>