A piece of iron wire is (9/10) meters long, (3/8) of it is used up for the first time, and (2/5) of it is used up for the second time, what fraction of the total length is left?
一根铁丝长(9/10)米，第一次用去它的(3/8)，第二次用去它的(2/5)，还剩全长的几分之几？
<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

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

<gadget id="calculator">1 - (3/8) - (2/5)</gadget>
<output>9/40 = around 0.225</output>

<result>9/40 = around 0.225</result>