A rope is used up (2/5) and there is (2/5) meters left. How long is the rope in meters?
一根绳子用去(2/5)后还剩(2/5)米，这根绳子长多少米．
<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">(2/5) / (3/5)</gadget>
<output>2/3 = around 0.666667</output>

<result>2/3 = around 0.666667</result>