To build a road, the original plan is to build 40 meters per day, which can be completed in 20 days. If you want to finish repairing 4 days ahead of schedule, how much will your daily work efficiency be increased by?
修一条路，原计划每天修40米，20天可以完成．如果要提前4天修完，每天的工作效率要提高百分之几？
<gadget id="calculator">40 * 20</gadget>
<output>800</output>

<gadget id="calculator">20 - 4</gadget>
<output>16</output>

<gadget id="calculator">800 / 16</gadget>
<output>50</output>

<gadget id="calculator">50 - 40</gadget>
<output>10</output>

<gadget id="calculator">10 / 40</gadget>
<output>1/4 = around 0.25</output>

<result>1/4 = around 0.25</result>