For a batch of steel, it takes 45 vehicles to load a small truck, and only 36 vehicles to load a large truck. It is known that each large truck loads 4 tons more than each small truck, so how many tons are there in this batch of steel?
一批钢材，用小卡车装载要45辆，用大卡车装载只要36辆．已知每辆大卡车比每辆小卡车多装4吨，那么这批钢材有多少吨？
<gadget id="calculator">1 / 36</gadget>
<output>1/36 = around 0.027778</output>

<gadget id="calculator">1 / 45</gadget>
<output>1/45 = around 0.022222</output>

<gadget id="calculator">(1/36) - (1/45)</gadget>
<output>1/180 = around 0.005556</output>

<gadget id="calculator">4 / (1/180)</gadget>
<output>720</output>

<result>720</result>