First cut off (1/5) of an iron wire, and then cut off (1/2) of it, how much of the iron wire is left.
一根铁丝先剪去它的(1/5)，再剪去它的(1/2)，还剩下这根铁丝的多少．
<gadget id="calculator">1 / 5</gadget>
<output>1/5 = around 0.2</output>

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

<gadget id="calculator">1 - (1/5) - (1/2)</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>