A wire is used up (2/5) for the first time, the remaining (2/3) is used up for the second time, and how much of the total length is used up for the second time.
一根电线第一次用去了(2/5)，第二次用去了余下的(2/3)，第二次用去了全长的多少．
<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 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">(3/5) * (2/3)</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>