After 40% of a piece of wood is used up, there is still 1.5 meters left. How many meters is the length of this piece of wood?
一根木料用去40%后，还剩1.5米，这根木料长多少米．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">1.5 / (3/5)</gadget>
<output>2.5</output>

<result>2.5</result>