A section of road was repaired on the first day (1/2), and the rest (1/2) was repaired on the second day. How much is the remaining length?
一段路，第一天修了(1/2)，第二天修了剩下的(1/2)，还剩全长的多少
<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>

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

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