For a batch of goods, (1/4) of the total number was transported for the first time, and (1/5) of the total number was transported for the second time. The first time transported 30 tons more than the second time. How many tons is this shipment in total?
一批货物，第一次运走总数的(1/4)，第二次又运走总数的(1/5)，第一次运的比第二次多30吨．这批货物共有多少吨？
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

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

<gadget id="calculator">(1/4) - (1/5)</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">30 / (1/20)</gadget>
<output>600</output>

<result>600</result>