The cement plant planned to produce 400 tons of cement last month, but actually produced 520 tons. What percentage was the overproduction?
水泥厂上个月计划生产水泥400吨，实际生产了520吨，超产了百分之几？
<gadget id="calculator">520 - 400</gadget>
<output>120</output>

<gadget id="calculator">120 / 400</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>