Exercise 3, a batch of steel products needs 35 vehicles to be loaded in small cars, and only 30 vehicles are used to load them in large vehicles. Each small vehicle can be loaded with 3 tons less than the large vehicle. How many tons are there in this batch of steel products?
练习3，一批钢材，用小车装，要用35辆，用大车装只用30辆，每辆小车比大车少装3吨，这批钢材有多少吨？
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">1 / 35</gadget>
<output>1/35 = around 0.028571</output>

<gadget id="calculator">(1/30) - (1/35)</gadget>
<output>1/210 = around 0.004762</output>

<gadget id="calculator">3 / (1/210)</gadget>
<output>630</output>

<result>630</result>