A wire is 10 meters long, if (2/5) is used up, how many meters are left?
一根铁丝长10米，用去(2/5)，还剩多少米．
<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">10 * (3/5)</gadget>
<output>6</output>

<result>6</result>