Half a barrel of oil, after using the degreased (2/5), there are 27 liters left, the bottom area of the barrel is 9dm**2, what is the height of the oil barrel.
半桶油，用去油的(2/5)以后，还剩27升，桶的底面积9dm**2，油桶的高是多少．
<gadget id="calculator">2 / 5</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">27 / (3/5)</gadget>
<output>45</output>

<gadget id="calculator">45 / 9</gadget>
<output>5</output>

<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<result>10</result>