The distance from this mountain to that mountain is 720 meters. Xiaohua's average speed is 60 meters per minute when going up the mountain and 0/20 meters per minute when going down the mountain. What is the average speed of small flowers going back and forth?
Solution: T = 720 ÷ 60 = 12 minutes.
T = 720 ÷ 120 = 6 minutes.
Average speed = 720× 2 ÷ (12+6) =1440 ÷18 = 80m/min.
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