A train travels from Hanoi station and Hue station. The first half of the train travels at 70km/h. Half
the rest of the time the train travels at speed v2. Know your average speed. trains a trên cả quãng đường là 60 km/h.Tính v2
A.60 km/h B.50 km/h C.58,33 km/h D.55 km/h
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Sinh Học lớp 12
