Guanghua Battery Factory produced 480 boxes of batteries in October, an increase of 80 boxes compared with September. What percentage increase?
光华电池厂十月份生产电池480箱，比九月份增产80箱，增产了百分之几？
<gadget id="calculator">480 - 80</gadget>
<output>400</output>

<gadget id="calculator">80 / 400</gadget>
<output>1/5 = around 0.2</output>

<result>1/5 = around 0.2</result>