A job started on June 1 and was originally scheduled to be completed in one month. During the actual construction, the task was completed on June 20. According to this calculation, how much was overfulfilled by June 30.
一项工作，6月1日开工，原定一个月完成．实际施工时，6月20日完成任务，照这样计算，到6月30日超额完成多少．
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">(1/20) * 30</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">(3/2) - 1</gadget>
<output>1/2 = around 0.5</output>

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

<result>1/2 = around 0.5</result>