Một ngọn hải đăng được đặt ở vị trí A cách bờ biển...
Câu hỏi: Một ngọn hải đăng được đặt ở vị trí A cách bờ biển một khoảng AB = 5km. Trên bờ biển có một cái kho ở vị trí C cách B một khoảng 7km. Người canh hải đăng có thể chèo đò từ điểm A đến địa điểm M trên bờ biển với vận tốc 4km/h, rồi đi bộ đến C với vận tốc 6km/h. Hỏi cần đặt vị trí của M cách B một khoảng bằng bao nhiêu km để người đó đến kho nhanh nhất?![](data:image/png;base64,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)
A 4,5 km
B 5,5 km
C \(2\sqrt{5}km\)
D \(\sqrt{5}km\)
Câu hỏi trên thuộc đề trắc nghiệm
Đề thi thử THPT QG môn Toán trường THPT Chuyên Trần Phú - Hải Phòng - lần 1 - năm 2018 (có lời giải chi tiết)