The fertilizer factory produced 400 tons of fertilizer in the first quarter, which was 20% less than that in the second quarter. How many tons of fertilizer was produced in the second quarter?
化肥厂第一季度生产化肥400吨，比第二季度少20%，第二季度生产化肥多少吨？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">400 / (4/5)</gadget>
<output>500</output>

<result>500</result>