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duonganh35
2 năm trước
Một chiếc tàu thủy chuyển động đều trên sông với vận tốc v1 = 35km/h gặp 1 sà lan dài 250 m đi song song ngược chiều với vận tốc v2 = 20km/h. Trên boong tàu có 1 thủy thủ đi từ mũi đến lái với vận tốc v3 = 5km/h. Hỏi người đó thấy đoàn sà lan đi ngang qua mặt mình trong bao lâu. Trong thời gian đó tàu thủy đi được quãng đường dài bao nhiêu ? Coi như mặt nước đứng yên.
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