The school organized donations to the "Yushu, Qinghai" disaster area. The fifth grade students donated 420 yuan, which was 20% less than the sixth grade. How much did the sixth grade donate?
学校组织向"青海玉树"灾区捐款，五年级同学捐款420元，比六年级少20%，六年级捐款多少元？
<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">420 / (4/5)</gadget>
<output>525</output>

<result>525</result>