A piece of steel, the whole steel (1/5) was used for the first time, and the whole steel (2/5) was used for the second time, what fraction of the whole steel is left?
一根钢材，第一次用去了整根的(1/5)，第二次用去了整根的(2/5)，还剩下整根的几分之几？
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/5) - (2/5)</gadget>
<output>2/5 = around 0.4</output>

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