piece of steel, 40% of the total length is cut off for the first time, and (2/5)m is cut off for the second time, leaving half of the total length. How many meters is this steel?
一根钢材，第一次截去全长的40%，第二次截去(2/5)m，还剩下全长的一半，这根钢材长多少米？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (1/2) - (2/5)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(2/5) / (1/10)</gadget>
<output>4</output>

<result>4</result>