A person covers the first 200 km at a speed of 50 km/h and the next 200 km at 70 km/h. Find its average speed in a journey of 400 km. A. 56.5 km/h B. 60.6 km/h C. 64.6 km/h D. 58.3 km/h

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Answer: (C) D

Explanation

Time = 200/50 + 200/70 = 4 + 20/7 = 48/7 hours. Average speed = 400 ÷ 48/7 = 2800/48 ≈ 58.3 km/h.