A tourist traveled by car. He covered 30% of the distance at a speed of 20…
A tourist traveled by car. He covered 30% of the distance at a speed of 20 km/h, 60% of the distance at a speed of 40 km/h, and the remaining distance at 10 km/h. What was his average speed for the whole journey?
Answer: 25 — Choose a convenient total distance (for percentages). Let the total distance be 100 km. Distance covered at 20 km/h: 30% of 100 km = 30 km. Time = 30/20 = 1.5…
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Correct answer: 25
Choose a convenient total distance (for percentages). Let the total distance be 100 km.
Distance covered at 20 km/h: 30% of 100 km = 30 km. Time = 30/20 = 1.5 hours.
Distance covered at 40 km/h: 60% of 100 km = 60 km. Time = 60/40 = 1.5 hours.
Remaining distance at 10 km/h: 10% of 100 km = 10 km. Time = 10/10 = 1 hour.
Total time = 1.5 + 1.5 + 1 = 4 hours.
Average speed = total distance / total time = 100 / 4 = 25 km/hr.
Therefore the average speed for the whole journey is 25 km/hr.