The car runs along the Panshan Highway from the foot of the mountain to the top of the mountain, with a total length of 1200 meters. It is known that the speed of the car going up the mountain is 100 meters per minute, and it takes 8 minutes to go down the mountain. What is the average speed of the car going back and forth in meters per minute?
汽车沿盘山公路从山脚到山顶，全长1200米．已知汽车上山的速度是每分钟100米，下山用了8分钟，则汽车往返一次的平均速度是每分钟多少米．
<gadget id="calculator">1_200 + 1_200</gadget>
<output>2_400</output>

<gadget id="calculator">1_200 / 100</gadget>
<output>12</output>

<gadget id="calculator">12 + 8</gadget>
<output>20</output>

<gadget id="calculator">2_400 / 20</gadget>
<output>120</output>

<result>120</result>