If (2/5) is cut off from a rope, exactly 4 meters will be cut off. If (3/10) is cut off, how many meters will be cut off?
一根绳子截去(2/5)，正好截去了4米，如果截去(3/10)，要截去多少米．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">4 / (2/5)</gadget>
<output>10</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">10 * (3/10)</gadget>
<output>3</output>

<result>3</result>