A piece of iron wire, use up the full length (1/2) for the first time, and use up the remaining (1/2) for the second time, how much of the full length is left?
一根铁丝，第一次用去全长的(1/2)，第二次用去余下的(1/2)，还剩下全长的多少？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

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

<gadget id="calculator">(1/2) * (1/2)</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>