The sixth grade students participated in the tree planting activity. They completed 20% of the plan on the first day, and planted 280 trees on the second day. The ratio of the number of trees planted to the number of planned trees was 2:5. How many trees did the sixth grade plan to plant?
六年级同学参加植树活动，第一天完成计划的20%，第二天植了280棵，已经植的棵数与计划植树的棵数比是2：5，六年级计划植树多少棵？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(2/5) - (1/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">280 / (1/5)</gadget>
<output>1_400</output>

<result>1_400</result>