A project was planned to be completed in 15 days, but the task was completed 5 days ahead of schedule. How much has the work efficiency increased?
一项工程，计划用15天完成，结果提前5天完成任务．工作效率提高了百分之几？
<gadget id="calculator">15 - 5</gadget>
<output>10</output>

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

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) - (1/15)</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/30) / (1/15)</gadget>
<output>1/2 = around 0.5</output>

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