A train moves 60 km at 30 km/h, halts for 1h, and then covers 90 km at 45 km/h. What is the average speed over the entire journey?
30 km/h
Average speed = total distance covered ÷ total time taken. The total time includes the time spent at the halt, because the journey is not over during the stop.
Time for the first part = 60 ÷ 30 = 2 h. Time for the second part = 90 ÷ 45 = 2 h. Halt = 1 h. So the total time = 2 + 1 + 2 = 5 h.
Total distance = 60 + 90 = 150 km. So the average speed = 150 ÷ 5 = 30 km/h.
Check: at 30 km/h for 5 h the train would cover 30 × 5 = 150 km, which equals 60 km + 90 km, so the average speed is consistent with the whole journey.
Hence, 30 km/h.
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