A man jogs at 6 mph over a certain distance and walks hack over the same route a

游客2024-08-10  18

问题 A man jogs at 6 mph over a certain distance and walks hack over the same route at 4 mph. What is his average speed for the journey?

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答案 4.8mph

解析 (mph英里/小时。设单程距离为x,平均速度=总距离/总时间=2x/(x/6+x/4)=4.8。)  
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