A piece of wire is (2/5) meters long. After cutting off (1/5), and then connecting 4 meters, the result is how many meters longer than the original wire.
一段电线，长(2/5)米，截去(1/5)后，再接上4米，结果比原来电线长多少米．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(2/5) * (4/5)</gadget>
<output>8/25 = around 0.32</output>

<gadget id="calculator">4 - (2/5)</gadget>
<output>18/5 = around 3.6</output>

<gadget id="calculator">(8/25) + (18/5)</gadget>
<output>98/25 = around 3.92</output>

<result>98/25 = around 3.92</result>