A packing box is 6 decimeters long and 4 decimeters wide, which accounts for exactly 20% of the total length of the packing box. What is the height of this packing box.
一个包装箱长6分米，宽4分米，正好占这个包装箱棱长总数的20%．这个包装箱的高是多少．
<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">10 / (1/5) / 4</gadget>
<output>25/2 = around 12.5</output>

<gadget id="calculator">(25/2) - 10</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>