A chemical fertilizer factory planned to complete a task in 14 days. Due to improved technology, the task was completed 4 days ahead of schedule. How many percent did the daily work efficiency increase?
某化肥厂计划用14天完成一项任务，由于改进技术，提前4天完成了任务，求每天工作效率提高了百分之几？
<gadget id="calculator">14 - 4</gadget>
<output>10</output>

<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 14</gadget>
<output>1/14 = around 0.071429</output>

<gadget id="calculator">(1/10) - (1/14)</gadget>
<output>1/35 = around 0.028571</output>

<gadget id="calculator">(1/35) / (1/14)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>