3 tons is 40% less than how many tons.
3吨比多少吨少40%．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">3 / (3/5)</gadget>
<output>5</output>

<result>5</result>