The road construction team wants to build a 500-meter-long railway, and 80% of it has been repaired. How many meters are left to be repaired?
修路队要修一条长500米的铁路，已经修了80%，还剩多少米没有修？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 - (4/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">500 * (1/5)</gadget>
<output>100</output>

<result>100</result>