Master Li planned to make a batch of parts in June, and completed 55% of the planned tasks in the first half of the month, and 60% of the planned tasks in the second half of the month. By what percentage did Master Li overfulfill the planned tasks?
李师傅六月份计划做一批零件，上半月完成计划任务的55%，下半月完成计划任务的60%，李师傅超额完成计划任务的百分之几？
<gadget id="calculator">55 / 100</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">60 / 100</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(3/5) - 1</gadget>
<output>-2/5 = around -0.4</output>

<gadget id="calculator">(11/20) + (-2/5)</gadget>
<output>3/20 = around 0.15</output>

<result>3/20 = around 0.15</result>