A piece of iron wire, 40% is cut off for the first time, and 1/4 is cut off for the second time, leaving 49 meters. How long is this iron wire?
一根铁丝，第一次剪去40%，第二次剪去(1/4)，还剩49米，这根铁丝原来有多长？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (2/5) - (1/4)</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">49 / (7/20)</gadget>
<output>140</output>

<result>140</result>