Tingting's home is 600 meters away from the school. Tingting rode a bicycle from home to school. After riding for 20 minutes, she was 200 meters away from the school. How many meters per branch does Tingting average?
婷婷家距学校600米，婷婷骑自行车从家出发向学校走，骑了20分钟，距学校还剩200米，婷婷平均每分行多少米？
<gadget id="calculator">600 - 200</gadget>
<output>400</output>

<gadget id="calculator">400 / 20</gadget>
<output>20</output>

<result>20</result>