The Young Pioneers participated in the tree planting activities. Wang Ming said: "We planted 30% of the total number of saplings on the first day, and 100 trees on the second day. We planted exactly half of the total number of saplings in two days." Please do the math: How many trees will the Young Pioneers plant in total?
少先队参加植树活动．王明说："我们第一天种了树苗总数的30%，第二天种了100棵，两天刚好种了树苗总数的一半．"请你算一算：少先队一共要种多少棵树？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(1/2) - (3/10)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">100 / (1/5)</gadget>
<output>500</output>

<result>500</result>