There are 40 species of birch trees in the world, and the species of birch forests in my country account for (11/20). How many species of birch trees are there in other countries than in my country?
全世界有桦树40种，我国桦树林种类占其中的(11/20)．其他国家的桦树种类比我国少多少种？
<gadget id="calculator">11 / 20</gadget>
<output>11/20 = around 0.55</output>

<gadget id="calculator">1 - (11/20)</gadget>
<output>9/20 = around 0.45</output>

<gadget id="calculator">(11/20) - (9/20)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">40 * (1/10)</gadget>
<output>4</output>

<result>4</result>