A factory completed the monthly plan (3/5) in the first half of May, and completed the monthly plan (4/7) in the second half of May. What percentage of the monthly plan was overfulfilled in May?
一个工厂五月份上半月完成月计划的(3/5)，下半月完成月计划的(4/7)，五月份超额完成月计划的几分之几？
<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">4 / 7</gadget>
<output>4/7 = around 0.571429</output>

<gadget id="calculator">(4/7) - 1</gadget>
<output>-3/7 = around -0.428571</output>

<gadget id="calculator">(3/5) + (-3/7)</gadget>
<output>6/35 = around 0.171429</output>

<result>6/35 = around 0.171429</result>