When the flag was raised on Monday, the students stood in a column. There were 20 people standing in front of Xiao Ming and 11 people standing behind him. If the distance between two adjacent people was 4 decimeters, how many meters is the length of Xiao Ming's column?
星期一升旗时同学们按纵队站立，小明前面站有20人，后面有11人，如果每相邻两人间隔4分米，小明所在的纵队长是多少米？
<gadget id="calculator">1 - 1</gadget>
<output>0</output>

<gadget id="calculator">20 + 11 + 0</gadget>
<output>31</output>

<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">31 * (2/5)</gadget>
<output>62/5 = around 12.4</output>

<result>62/5 = around 12.4</result>