There are a bunch of goods, which need to be transported 20 times by large trucks, and 30 times by small trucks. Each large truck carries 3 tons more than the small truck. How many tons is this pile of goods?
有一堆货物，用大卡车运，要运20次；用小卡车运，要运30次．每辆大卡车比小卡车多运3吨．这堆货物有多少吨？
<gadget id="calculator">1 / 20</gadget>
<output>1/20 = around 0.05</output>

<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">(1/20) - (1/30)</gadget>
<output>1/60 = around 0.016667</output>

<gadget id="calculator">3 / (1/60)</gadget>
<output>180</output>

<result>180</result>