There are 5 kg of oil. Use up all (2/5), how many kilograms are left.
有5千克油．用去全部的(2/5)，还剩多少千克．
<gadget id="calculator">2 / 5</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">5 * (3/5)</gadget>
<output>3</output>

<result>3</result>