The distance from Zhang Yong's home to the school is 1.2 kilometers. One day it took him 20 minutes to go to school and 30 minutes to get home from school. What is his average round trip speed in km/min
张勇家到学校的路程为1.2千米．有一天他上学用了20分钟，放学回家用了30分钟．他往返的平均速度是多少千米∕分
<gadget id="calculator">20 + 30</gadget>
<output>50</output>

<gadget id="calculator">2 / 50</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">1.2 * (1/25)</gadget>
<output>0.048</output>

<result>0.048</result>